Android: Implement thread, semaphore, shared memory API functions. Implement dwmain() entrypoint and include dwtest.c in the build. Like on iOS dw_main() doesn't actually run the message loop... So wait for dw_main() to be called and return to the JVM.

# Set these here to change the version for all platforms
DW_MAJOR_VERSION=3
DW_MINOR_VERSION=2