mesa: Remove GLXContextID typedef from glx.h.

Fixes this build error.

  CC     clientattrib.lo
In file included from ../../include/GL/glx.h:333,
                 from glxclient.h:45,
                 from clientattrib.c:32:
../../include/GL/glxext.h:275: error: redefinition of typedef ‘GLXContextID’
../../include/GL/glx.h:171: note: previous declaration of ‘GLXContextID’ was here

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=70591
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
glsl: Initialize per_vertex_accumulator::fields.

Fixes "Uninitialized pointer field" defect reported by Coverity.

Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Paul Berry <stereotype441@gmail.com>