Fixed bug 2490 - [PATCH] Fix options for android builds

Ben Boeckel

Currently, to override the SUPPORT_* options, one must patch SDL_mixer's Android.mk to set them to false. This patch makes it so that the user may set the options in the top-level jni/Android.mk file without having to patch SDL_mixer.
Fixed bug 2491 - [PATCH] Force LOCAL_ARM_MODE for android builds

Ben Boeckel

SDL_mixer only builds with the LOCAL_ARM_MODE := arm since the third-party libs do not support the THUMB extensions.
WinRT: added project files for Windows 8.0/RT use, with support for Ogg Vorbis

Various libraries from "externals/" were used, however no modifications were
made to the libraries.  If these libraries are updated, the paths inside the
project files (in VisualC-WinRT) will need to be updated.

TODO:
- write a script to update project file contents if and when an external library
  is updated.
- add project files for Windows Phone 8.0
- add project files for WinRT Universal (Windows 8.1, Windows Phone 8.1, etc.)
- add support for file formats other than Ogg Vorbis
- suppress build warnings when building external library code
- add a README.txt file to VisualC-WinRT/, outlining which directories are
  relevant to which project types (Windows 8.0/RT has one project type,
  Windows Phone 8.0 has another, WinRT universal has another)
WinRT: added project files for Windows Phone 8.0 use

File format support is currently limited to Ogg Vorbis.
WinRT: updated to use latest SDL/WinRT project structure
Update comment for Mix_HookMusicFinished

It was incorrectly stating that the hook only gets called if it's a "natural"
finish of the music.