glx: Fix the default values for GLXFBConfig attributes

The default values for GLX_DRAWABLE_TYPE and GLX_RENDER_TYPE are
GLX_WINDOW_BIT and GLX_RGBA_BIT respectively, as specified in
the GLX 1.4 specification.

This fixes the glx-choosefbconfig-defaults piglit test.

Cc: "9.2 10.0 10.1" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
(cherry picked from commit f41c2f6c332ae9b9784ac924b718963a1086cb85)
glx: Fix the GLXFBConfig attrib sort priorities

The sort priorites for GLX_SAMPLES and GLX_SAMPLE_BUFFERS are
not defined in GL_ARB_multisample, but they are defined in
the GLX 1.4 specification.

Cc: "9.2 10.0 10.1" <mesa-stable@lists.freedesktop.org>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
(cherry picked from commit 3616e862f29838d73fcb05134b1dc628da499fc2)