egl: update headers

egl: update headers

Update to revision 15052.

EGL_MESA_drm_image is now official.  But apparently we have our own extension
to it and we need this in eglmesaext.h:

  #ifdef EGL_MESA_drm_image
  /* Mesa's extension to EGL_MESA_drm_image... */
  #ifndef EGL_DRM_BUFFER_USE_CURSOR_MESA
  #define EGL_DRM_BUFFER_USE_CURSOR_MESA		0x0004
  #endif
  #endif

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>