GLX: fix out-of-bounds memory issue in indirect glAreTexturesResident()

GLX: fix out-of-bounds memory issue in indirect glAreTexturesResident()

See bug 18445.
When getting array results, __glXReadReply() always reads a multiple of
four bytes.  This can cause writing to invalid memory when 'n' is not a
multiple of four.

Special-case the glAreTexturesResident() functions now.
To fix the bug, we use a temporary buffer that's a multiple of four bytes
in length.

NOTE: this commit also reverts part of commit 919ec22ecf72aa163e1b97d8c7381002131ed32c
(glx/x11: Added some #ifdef GLX_DIRECT_RENDERING protection) which
directly edited the indirect.c file rather than the python generator!
I'm not repairing that issue at this time.