Currently only supports a subset of decode functions and likely only
works fully for java.
For java bindings:
The generated java source can be compiled and the class files added to
libwebp.jar.
The generated jni source can be compiled to, e.g., libwebp_jni.so, which
can then be loaded via System.loadLibrary("webp_jni").
Change-Id: I8225933cbaf85c9cfa4b78c2e5f167cee8b62408
