Revise some renamings of NOTES and README files

Some of the notes and readme files have been converted to markdown
format recently and renamed during this process. While adding the
.md extension was a natural step, switching to mixed cases was not
a change to the better, it gives them a ragged appearance:

     NOTES.ANDROID  => NOTES-Android.md
     NOTES.DJGPP    => NOTES-DJGPP.md
     NOTES.PERL     => NOTES-Perl.md
     NOTES.UNIX     => NOTES-Unix.md
     NOTES.VMS      => NOTES-VMS.md
     NOTES.VALGRIND => NOTES-Valgrind.md
     NOTES.WIN      => NOTES-Windows.txt
     README.ENGINE  => README-Engine.md
     README.FIPS    => README-FIPS.md

Moreover, the NOTES-Windows.txt file is the only file which has been
converted to markdown but has received a .txt file extension.
This doesn't make sense, because the OpenSSL users on Windows will
need to read the other markdown documents as well. Since they are
developers, we can trust them to be able to associate their favorite
editor with the .md extension.

In fact, having a comment at the beginning of the file saying that it
is in markdown format but we didn't dare to add the correct extension
in order not to overwhelm our Windows users can be interpreted either
as unintentionally funny or disrespectful ;-)

This commit suggests the following more consistent renaming:

     NOTES.ANDROID  => NOTES-ANDROID.md
     NOTES.DJGPP    => NOTES-DJGPP.md
     NOTES.PERL     => NOTES-PERL.md
     NOTES.UNIX     => NOTES-UNIX.md
     NOTES.VMS      => NOTES-VMS.md
     NOTES.VALGRIND => NOTES-VALGRIND.md
     NOTES.WIN      => NOTES-WINDOWS.md
     README.ENGINE  => README-ENGINES.md
     README.FIPS    => README-FIPS.md

(note the plural in README-ENGINES, anticipating a README-PROVIDERS)

Reviewed-by: Paul Dale <pauli@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/14042)

1 files changed, 90 insertions, 0 deletions

diff --git a/NOTES-ANDROID.md b/NOTES-ANDROID.md
new file mode 100644
index 0000000000..e1e7370d26
--- /dev/null
+++ b/NOTES-ANDROID.md
@@ -0,0 +1,90 @@
+NOTES FOR ANDROID PLATFORMS
+===========================
+
+ Requirement details
+ -------------------
+
+ Beside basic tools like perl and make you'll need to download the Android
+ NDK. It's available for Linux, macOS and Windows, but only Linux
+ version was actually tested. There is no reason to believe that macOS
+ wouldn't work. And as for Windows, it's unclear which "shell" would be
+ suitable, MSYS2 might have best chances. NDK version should play lesser
+ role, the goal is to support a range of most recent versions.
+
+ Configuration
+ -------------
+
+ Android is a cross-compiled target and you can't rely on `./Configure`
+ to find out the configuration target for you.  You have to name your
+ target explicitly; there are `android-arm`, `android-arm64`, `android-mips`,
+ `android-mip64`, `android-x86` and `android-x86_64` (`*MIPS` targets are no
+ longer supported with NDK R20+).
+
+ Do not pass --cross-compile-prefix (as you might be tempted), as it
+ will be "calculated" automatically based on chosen platform. However,
+ you still need to know the prefix to extend your PATH, in order to
+ invoke `$(CROSS_COMPILE)clang` [`*gcc` on NDK 19 and lower] and company.
+ (`./Configure` will fail and give you a hint if you get it wrong.)
+
+ Apart from `PATH` adjustment you need to set `ANDROID_NDK_ROOT` environment
+ to point at the `NDK` directory. If you're using a side-by-side NDK the path
+ will look something like `/some/where/android-sdk/ndk/<ver>`, and for a
+ standalone NDK the path will be something like `/some/where/android-ndk-<ver>`.
+ Both variables are significant at both configuration and compilation times.
+ The NDK customarily supports multiple Android API levels, e.g. `android-14`,
+ `android-21`, etc. By default latest API level is chosen. If you need to target
+ an older platform pass the argument `-D__ANDROID_API__=N` to `Configure`,
+ with `N` being the numerical value of the target platform version. For example,
+ to compile for Android 10 arm64 with a side-by-side NDK r20.0.5594570
+
+    export ANDROID_NDK_ROOT=/home/whoever/Android/android-sdk/ndk/20.0.5594570
+    PATH=$ANDROID_NDK_ROOT/toolchains/llvm/prebuilt/linux-x86_64/bin:$ANDROID_NDK_ROOT/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin:$PATH
+    ./Configure android-arm64 -D__ANDROID_API__=29
+    make
+
+ Older versions of the NDK have GCC under their common prebuilt tools
+ directory, so the bin path will be slightly different. EG: to compile
+ for ICS on ARM with NDK 10d:
+
+    export ANDROID_NDK_ROOT=/some/where/android-ndk-10d
+    PATH=$ANDROID_NDK_ROOT/toolchains/arm-linux-androideabi-4.8/prebuilt/linux-x86_64/bin:$PATH
+    ./Configure android-arm -D__ANDROID_API__=14
+    make
+
+ Caveat lector! Earlier OpenSSL versions relied on additional `CROSS_SYSROOT`
+ variable set to `$ANDROID_NDK_ROOT/platforms/android-<api>/arch-<arch>` to
+ appoint headers-n-libraries' location. It's still recognized in order
+ to facilitate migration from older projects. However, since API level
+ appears in `CROSS_SYSROOT` value, passing `-D__ANDROID_API__=N` can be in
+ conflict, and mixing the two is therefore not supported. Migration to
+ `CROSS_SYSROOT`-less setup is recommended.
+
+ One can engage clang by adjusting PATH to cover same NDK's clang. Just
+ keep in mind that if you miss it, Configure will try to use gcc...
+ Also, PATH would need even further adjustment to cover unprefixed, yet
+ target-specific, ar and ranlib. It's possible that you don't need to
+ bother, if binutils-multiarch is installed on your Linux system.
+
+ Another option is to create so called "standalone toolchain" tailored
+ for single specific platform including Android API level, and assign its
+ location to `ANDROID_NDK_ROOT`. In such case you have to pass matching
+ target name to Configure and shouldn't use `-D__ANDROID_API__=N`. `PATH`
+ adjustment becomes simpler, `$ANDROID_NDK_ROOT/bin:$PATH` suffices.
+
+ Running tests (on Linux)
+ ------------------------
+
+ This is not actually supported. Notes are meant rather as inspiration.
+
+ Even though build output targets alien system, it's possible to execute
+ test suite on Linux system by employing qemu-user. The trick is static
+ linking. Pass -static to Configure, then edit generated Makefile and
+ remove occurrences of -ldl and -pie flags. You would also need to pick
+ API version that comes with usable static libraries, 42/2=21 used to
+ work. Once built, you should be able to
+
+    env EXE_SHELL=qemu-<arch> make test
+
+ If you need to pass additional flag to qemu, quotes are your friend, e.g.
+
+    env EXE_SHELL="qemu-mips64el -cpu MIPS64R6-generic" make test