Prepare for Rust 2018.

  - This is the result of running `cargo fix --edition`, with some
    manual adjustments.

  - The vast majority of changes merely qualify module paths with
    'crate::'.

  - Two instances of adding an anonymous pattern to a trait's
    function.

  - `async` is a keyword in Rust 2018, and hence it needs to be
    escaped (e.g. in the case of the net::r#async module).

  - The manual adjustments were needed due to various shortcomings of
    the analysis employed by `cargo fix`, e.g. unexpanded macros,
    procedural macros, lalrpop grammars.

76 files changed, 788 insertions, 788 deletions

diff --git a/openpgp/examples/decrypt-with.rs b/openpgp/examples/decrypt-with.rs
index 75b886eb..6562b3db 100644
--- a/openpgp/examples/decrypt-with.rs
+++ b/openpgp/examples/decrypt-with.rs
@@ -8,9 +8,9 @@ use std::io;
 extern crate failure;
 extern crate sequoia_openpgp as openpgp;
 
-use openpgp::crypto::{KeyPair, SessionKey};
-use openpgp::constants::SymmetricAlgorithm;
-use openpgp::parse::{
+use crate::openpgp::crypto::{KeyPair, SessionKey};
+use crate::openpgp::constants::SymmetricAlgorithm;
+use crate::openpgp::parse::{
     Parse,
     stream::{
         DecryptionHelper,
diff --git a/openpgp/examples/encrypt-for.rs b/openpgp/examples/encrypt-for.rs
index 3fd1217c..9b35623b 100644
--- a/openpgp/examples/encrypt-for.rs
+++ b/openpgp/examples/encrypt-for.rs
@@ -5,10 +5,10 @@ use std::env;
 use std::io;
 
 extern crate sequoia_openpgp as openpgp;
-use openpgp::armor;
-use openpgp::constants::DataFormat;
-use openpgp::parse::Parse;
-use openpgp::serialize::stream::{
+use crate::openpgp::armor;
+use crate::openpgp::constants::DataFormat;
+use crate::openpgp::parse::Parse;
+use crate::openpgp::serialize::stream::{
     Message, LiteralWriter, Encryptor, EncryptionMode,
 };
 
diff --git a/openpgp/examples/generate-encrypt-decrypt.rs b/openpgp/examples/generate-encrypt-decrypt.rs
index 8a450d24..50159825 100644
--- a/openpgp/examples/generate-encrypt-decrypt.rs
+++ b/openpgp/examples/generate-encrypt-decrypt.rs
@@ -3,10 +3,10 @@
 use std::io::{self, Write};
 
 extern crate sequoia_openpgp as openpgp;
-use openpgp::crypto::SessionKey;
-use openpgp::constants::SymmetricAlgorithm;
-use openpgp::serialize::stream::*;
-use openpgp::parse::stream::*;
+use crate::openpgp::crypto::SessionKey;
+use crate::openpgp::constants::SymmetricAlgorithm;
+use crate::openpgp::serialize::stream::*;
+use crate::openpgp::parse::stream::*;
 
 const MESSAGE: &'static str = "дружба";
 
diff --git a/openpgp/examples/generate-sign-verify.rs b/openpgp/examples/generate-sign-verify.rs
index 70899c81..cc350a63 100644
--- a/openpgp/examples/generate-sign-verify.rs
+++ b/openpgp/examples/generate-sign-verify.rs
@@ -4,8 +4,8 @@ use std::io::{self, Write};
 
 extern crate failure;
 extern crate sequoia_openpgp as openpgp;
-use openpgp::serialize::stream::*;
-use openpgp::parse::stream::*;
+use crate::openpgp::serialize::stream::*;
+use crate::openpgp::parse::stream::*;
 
 const MESSAGE: &'static str = "дружба";
 
diff --git a/openpgp/examples/notarize.rs b/openpgp/examples/notarize.rs
index fd1c56b1..54c7fa79 100644
--- a/openpgp/examples/notarize.rs
+++ b/openpgp/examples/notarize.rs
@@ -5,7 +5,7 @@ use std::env;
 use std::io;
 
 extern crate sequoia_openpgp as openpgp;
-use openpgp::{
+use crate::openpgp::{
     armor,
     crypto,
     Packet,
@@ -13,7 +13,7 @@ use openpgp::{
     parse::{Parse, PacketParserResult},
     serialize::Serialize,
 };
-use openpgp::serialize::stream::{Message, LiteralWriter, Signer};
+use crate::openpgp::serialize::stream::{Message, LiteralWriter, Signer};
 
 fn main() {
     let args: Vec<String> = env::args().collect();
diff --git a/openpgp/examples/sign-detached.rs b/openpgp/examples/sign-detached.rs
index a4ee95ad..30620eb3 100644
--- a/openpgp/examples/sign-detached.rs
+++ b/openpgp/examples/sign-detached.rs
@@ -5,10 +5,10 @@ use std::io;
 extern crate rpassword;
 
 extern crate sequoia_openpgp as openpgp;
-use openpgp::armor;
-use openpgp::crypto;
-use openpgp::parse::Parse;
-use openpgp::serialize::stream::{Message, Signer};
+use crate::openpgp::armor;
+use crate::openpgp::crypto;
+use crate::openpgp::parse::Parse;
+use crate::openpgp::serialize::stream::{Message, Signer};
 
 fn main() {
     let args: Vec<String> = env::args().collect();
diff --git a/openpgp/examples/sign.rs b/openpgp/examples/sign.rs
index 637679ab..cfd9c136 100644
--- a/openpgp/examples/sign.rs
+++ b/openpgp/examples/sign.rs
@@ -4,11 +4,11 @@ use std::env;
 use std::io;
 
 extern crate sequoia_openpgp as openpgp;
-use openpgp::armor;
-use openpgp::crypto;
-use openpgp::constants::DataFormat;
-use openpgp::parse::Parse;
-use openpgp::serialize::stream::{Message, LiteralWriter, Signer};
+use crate::openpgp::armor;
+use crate::openpgp::crypto;
+use crate::openpgp::constants::DataFormat;
+use crate::openpgp::parse::Parse;
+use crate::openpgp::serialize::stream::{Message, LiteralWriter, Signer};
 
 fn main() {
     let args: Vec<String> = env::args().collect();
diff --git a/openpgp/examples/statistics.rs b/openpgp/examples/statistics.rs
index 00bbadba..9bfdd94e 100644
--- a/openpgp/examples/statistics.rs
+++ b/openpgp/examples/statistics.rs
@@ -9,10 +9,10 @@
 
 use std::env;
 extern crate sequoia_openpgp as openpgp;
-use openpgp::Packet;
-use openpgp::constants::SignatureType;
-use openpgp::packet::{user_attribute, BodyLength, Tag};
-use openpgp::parse::{Parse, PacketParserResult, PacketParser};
+use crate::openpgp::Packet;
+use crate::openpgp::constants::SignatureType;
+use crate::openpgp::packet::{user_attribute, BodyLength, Tag};
+use crate::openpgp::parse::{Parse, PacketParserResult, PacketParser};
 
 fn main() {
     let args: Vec<String> = env::args().collect();
@@ -95,7 +95,7 @@ fn main() {
                     for (_offset, len, sub) in sig.hashed_area().iter()
                         .chain(sig.unhashed_area().iter())
                     {
-                        use openpgp::packet::signature::subpacket::*;
+                        use crate::openpgp::packet::signature::subpacket::*;
                         let i = u8::from(sub.tag) as usize;
                         sigs_subpacket_tags_count[i] += 1;
                         if let SubpacketValue::Unknown(_) = sub.value {
@@ -116,8 +116,8 @@ fn main() {
                 },
 
                 Packet::UserAttribute(ref ua) => {
-                    use user_attribute::Subpacket;
-                    use user_attribute::Image;
+                    use crate::user_attribute::Subpacket;
+                    use crate::user_attribute::Image;
                     for subpacket in ua.subpackets() {
                         match subpacket {
                             Ok(Subpacket::Image(i)) => match i {
@@ -215,7 +215,7 @@ fn main() {
                   ----------------------");
 
         for t in 0..256 {
-            use openpgp::packet::signature::subpacket::SubpacketTag;
+            use crate::openpgp::packet::signature::subpacket::SubpacketTag;
             let count = sigs_subpacket_tags_count[t];
             let size_count = sigs_subpacket_tags_size_count[t];
             let tag_name = format!("{:?}", SubpacketTag::from(t as u8));
diff