Added in a check for x86 and x86_64 branches of android

Added in $(OS) checks to see if we're running on windows or *nix

Added a default location for android ndks and sdks at /usr/lib/android

* added multi channel sound replay to raudio
added -fPIC to Makefile for Linux
added simple lighting and audio multi channel to examples Makefile

* not properly reporting audio buffer pool size...

With v2.5.0 out, increment API_VERSION, so binaries dynamically linked
against the released raylib aren't accidentally paired with a development
or later released raylib that may be incompatible.

From the Clang documentation[1]:
> -x<language>, --language <arg>, --language=<arg>
> Treat subsequent input files as having type <language>

Follow the advice. Fixes #840.
[1]: https://clang.llvm.org/docs/ClangCommandLineReference.html

This reverts #841 commit 97160fd970.

Some minor tweaks

Found some issues when building for web using latest emscripten 1.38.30, traced the error and found that eglGetProcAdress does not return function pointers for VAO functionality, supported by extension.

It requires more investigation but now it works (avoiding VAO usage)

The idea is supporting additional raygui and physac modules building with raylib but those modules are distributed as header-only libraries and it makes a bit dificult to build them inside raylib...

Renamed flags for convenience.

Planning to promote raudio module as a simple and easy-to-use front-end for the amazing mini_al library, so the name change.

Name comes from raylib-audio but in spanish it also remembers to word "raudo", meaning  "very fast", an analogy that fits perfectly to the usefulness and performance of the library!

Consequently, raylib version has been bumped to 2.4-dev.

Solves audio cracking issues

Added android_native_app_glue module to raylib compilation instead of
compiling it as static lib at apk generation.

From 2019 64bit support will be mandatory to publish an Android app.
Google plans to require that new apps target Oreo (API level 26) in
August of 2018.

Please do this whenever necessary. And adapt it before releasing a new
RC. The RC should already have the correct one.

Now defaults to Clang, ARM64 and API 21

Review raylib_icon resource

...PLATFORM_ANDROID on Windows, using MinGW-w64 (x86) provided Make (GCC
7.2)