GLES/gl.h has historically provided some typedefs that are not
used in the API itself. Restore these typedefs that were lost to
avoid breaking applications.
These seem to be the only typedefs removed in the update.
Fixes: 7fd08177 "Update Khronos-supplied headers"
[Eric: added a big warning to revert this patch when pulling the updated header]
Signed-off-by: Eric Engestrom <email@example.com>