Android: Removed all unnecessary dependencies on C++.

C++ is a bit of a minefield on Android. Much functionality still doesn't work, and Android can't decide on which C++ standard library to use, so it provides 3 different ones, all of which are incompatible with each other. (It looks like clang is coming too which will add a new compiler and a 4th standard library.)

As middleware, SDL might be distributed as a binary and intermixed with other projects already using C++. If C++ is intermixed in a bad way, bad things will happen. Removing dependencies on C++ will avoid this problem and downstream users won't have to worry/care.

--HG--
rename : src/core/android/SDL_android.cpp => src/core/android/SDL_android.c
rename : src/main/android/SDL_android_main.cpp => src/main/android/SDL_android_main.c