Enable nonl() mode for ncurses. closes #362.

This patch is based on the patch from Mike Frysinger, archived from
the old trac system at:
https://gitlab.com/muttmua/trac-tickets/-/blob/master/attachments/3494/mutt-enter-return-hg-6658.patch

This version creates a new key symbol, <KeypadEnter> for the KEY_ENTER
value returned by getch().  According to Vincent Lefèvre's research,
that corresponds to the "key pad" Enter key.  If KEY_ENTER is not
defined, it binds the symbol to "\n".  It does this after the
KeyNames[] definitions of <Enter> and <Return> so they remain the
default shown by <what-key>.

Since Mutt already accepts KEY_ENTER at the y/n prompt, add it for all
the built-in operations too.

Bindings with "\r" and "\n" in the binding_t structures don't need
"<enter>" and "<return>" to be re-specified in km_init(), so remove
those.  Instead add the "<KeypadEnter>" bindings there.

Remove unnecessary Alias menu bindings for OP_GENERIC_SELECT_ENTRY in
km_init().

As a note: I don't believe non-extended key symbol bindings need to be
bound inside km_init().  I'm not clear why this was done, or what
purpose it serves.  I'll do a bit more research, but if I can't
uncover any issues, will move them inside the binding_t structures in
another commit.

2 files changed, 29 insertions, 1 deletions

diff --git a/doc/gen-map-doc b/doc/gen-map-doc
index 4f58f13f..a58961b4 100644
--- a/doc/gen-map-doc
+++ b/doc/gen-map-doc
@@ -35,7 +35,8 @@ while (<STDIN>) {
     $binding =~ s/^\\(0\d+)$/'^'.chr(64+oct($1))/e;
     $binding =~ s/^\\(0\d+)(.)/'^'.chr(64+oct($1)) ." $2"/e;
     $binding =~ s/\\t/&lt;Tab&gt;/;
-    $binding =~ s/M_ENTER_S/&lt;Return&gt;/;
+    $binding =~ s/\\r/&lt;Return&gt;/;
+    $binding =~ s/\\n/&lt;Enter&gt;/;
     $binding =~ s/NULL//;
     die "unknown key $binding" if $binding =~ /\\[^\\]|<|>/;
     die "unknown OP $op" unless $OPS{$op};
diff --git a/doc/manual.xml.head b/doc/manual.xml.head
index c4e7427e..f2d7760d 100644
--- a/doc/manual.xml.head
+++ b/doc/manual.xml.head
@@ -2767,6 +2767,7 @@ addition, <emphasis>key</emphasis> may be a symbolic name as shown in
 <row><entry>&lt;insert&gt;</entry><entry>Insert</entry></row>
 <row><entry>&lt;enter&gt;</entry><entry>Enter</entry></row>
 <row><entry>&lt;return&gt;</entry><entry>Return</entry></row>
+<row><entry>&lt;keypadenter&gt;</entry><entry>Enter key on numeric keypad</entry></row>
 <row><entry>&lt;home&gt;</entry><entry>Home</entry></row>
 <row><entry>&lt;end&gt;</entry><entry>End</entry></row>
 <row><entry>&lt;space&gt;</entry><entry>Space bar</entry></row>
@@ -2834,6 +2835,32 @@ specified key sequence.
   </para>
 </sect2>
 
+<sect2 id="crlf">
+  <title>Enter versus Return</title>
+
+  <para>
+    Prior to version 2.2, Mutt used a default ncurses mode
+    (<quote><literal>nl()</literal></quote>).  This mode maps keyboard
+    input of either <literal>&lt;Enter&gt;</literal> or
+    <literal>&lt;Return&gt;</literal> to the same value, which Mutt
+    interpreted as <literal>&lt;Return&gt;</literal> internally.
+  </para>
+  <para>
+    However, starting in version 2.2, this mode is turned off,
+    allowing <literal>&lt;Return&gt;</literal> and
+    <literal>&lt;Enter&gt;</literal> to be mapped separately, if
+    desired.  The default keyboard mappings set both, but you can
+    override this or create new bindings with one or the other (or
+    both).
+  </para>
+  <para>
+    Note that in terminal application, such as Mutt,
+    <literal>&lt;Enter&gt;</literal> is the same as <quote>\n</quote>
+    and <literal>^J</literal>; while <literal>&lt;Return&gt;</literal>
+    is the same as <quote>\r</quote> and <literal>^M</literal>.
+  </para>
+</sect2>
+
 </sect1>
 
 <sect1 id="cd">