Move GLES20 source into standard locations Move Khronos headers into their respective components, to be exported by each. Remove hostthreadadapter as nothing outside of the vghwapiwrapper, which now contains the code, needs it

/*
 * This is just an RC_INVOKED guard for the real varargs.h
 * fixincluded in gcc system dir.  One day we will delete this file.
 */
#ifndef RC_INVOKED
#include_next<varargs.h>
#endif