Have __glImageSize handle format GL_DEPTH_STENCIL_NV the same way as the server does

There is a mismatch between the way the X server and GLX library
calculates the image size for format GL_DEPTH_STENCIL(|_NV|_EXT)

See https://bugs.freedesktop.org/show_bug.cgi?id=30102

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
1 file changed