mesa/image: Make _mesa_clip_readpixels() work with renderbuffers
mesa/image: Make _mesa_clip_readpixels() work with renderbuffers

v2: Use gl_renderbuffer::{Width,Height} (Jason)

Cc: "11.0 11.1" <59f39c0db42d4479a46b02d4d2bc11120e37bb44@lists.freedesktop.org>
Signed-off-by: Nanley Chery <d78cd5d33e98a5581566f188959f731bd0b1c0fd@intel.com>
Reviewed-by: Ian Romanick <2b237cafb16dc45038e85df6c85e74e6d899eba9@intel.com>
Reviewed-by: Brian Paul <3cb4e1df5ec4da2c7c4af7c52cec8cf340a55a10@vmware.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler