Add __ANDROID_API_[STU]__ definitions

Bring the host_init_stubs.h header file in sync with the
<android/api-level.h> header file.

Change-Id: I0d344b5f89f909e5315a0075773efd0b725a72a4
Signed-off-by: Bart Van Assche <bvanassche@google.com>