Temporary fix for bug 2494 - Crashes due to the non thread-safe SDL_malloc/SDL_free on Windows

We'll define USE_LOCKS as a temporary fix until an alternative like ptmalloc, jemalloc, or nedmalloc can be investigated.
http://www.malloc.de/en/
http://www.canonware.com/jemalloc/
http://www.nedprod.com/programs/portable/nedmalloc/

SDL allocates memory very infrequently, so this is probably a decent fix for a while.
Show  android video or android audio if detected in autotools summary.
Export android jni functions even when build with -fvisibility=hidden flag
__ANDROID__ is the correct macro to check for an android system.ANDROID is only defined in NDK build system (.mk) and not in the standalone NDK.
A few more ANDROID for __ANDROID__ replacements