i965/sync: Replace prefix 'intel_sync' -> 'intel_gl_sync'

i965/sync: Replace prefix 'intel_sync' -> 'intel_gl_sync'

I'm about to implement DRI2_Fenc in intel_syncobj.c.  To prevent
madness, we need to prefix functions for GL_ARB_sync with 'gl' and
functions for DRI2_Fence with 'dri'. Otherwise, the file will become
a jumble of similiarly named functions.

For example:
    old-name:      intel_client_wait_sync()
    new-name:      intel_gl_client_wait_sync()
    soon-to-come:  intel_dri_client_wait_sync()

I wrote this renaming commit separately from the commit that implements
DRI2_Fence because I wanted the latter diff to be reviewable.

Reviewed-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>