configure.ac: strip _GNU_SOURCE from llvm-config output

Mesa already defines _GNU_SOURCE for glibc based systems
and defining _GNU_SOURCE will break the Mesa build
on other systems such as OpenBSD.

Signed-off-by: Jonathan Gray <jsg@jsg.id.au>
(cherry picked from commit 3736bea75573090085d89743b66a334150403828)
use gsed where non posix 'end of word' escape is used

(cherry picked from commit c588dddaa3702f3b5d0e4c90c71e56d693774798)
OpenBSD ports llvm is now a 3.5 snapshot from 20140228

avoid llvm 3.5 codepaths that use changes made after this date

(cherry picked from commit 1633831b047c62a1f119858b03eb6ef73f2f7f49)
add -lgbm to EGL

CVSROOT:        /cvs
Module name:    xenocara
Changes by:     landry@cvs.openbsd.org  2014/07/14 04:12:16

Modified files:
        dist/Mesa/src/egl/main: egl.pc.in

Log message:
Add -lgbm to Libs as a temporary workaround, since EGL has unknown
symbols from libgbm, and that breaks www/webkit (and probably all the 23
ports linking against EGL, which now probably need WANTLIB fixes..)

with/ok matthieu@

(cherry picked from commit 39da1051471c90d241918c7f645a7ef78b4f031d)
radeonsi: Don't use anonymous struct trick in atom tracking

I'm somewhat impressed that current gccs will let you do this, but
sufficiently old ones (including 4.4.7 in RHEL6) won't.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Signed-off-by: Adam Jackson <ajax@redhat.com>
(cherry picked from commit 74388dd24bc7fdb9e62ec18096163f5426e03fbf)