glx: drop GLX_LIBS from X server and workaround sdksyms.

We've had reports of two copies of the GLX bits, one in the server
and one in libglx.so causing problems, I didn't understand why the
X server needed a copy so drop it, however then we have to fix a missing
GlxExtensionInit that comes from sdksyms, so work around it by moving
that one declaration into a header that sdksyms doesn't scan.

Thanks to Jon Turney for debugging the actual problem.
(copyright header from extinit.h that seems most appropriate put on top).

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=52402
Tested-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Daniel Stone <daniel@fooishbar.org>
Tested-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

include/glx_extinit.h

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 1994-2003 The XFree86 Project, Inc.  All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of
+ * this software and associated documentation files (the "Software"), to deal in
+ * the Software without restriction, including without limitation the rights to
+ * use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+ * of the Software, and to permit persons to whom the Software is furnished to do
+ * so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FIT-
+ * NESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+ * XFREE86 PROJECT BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+ * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Except as contained in this notice, the name of the XFree86 Project shall not
+ * be used in advertising or otherwise to promote the sale, use or other dealings
+ * in this Software without prior written authorization from the XFree86 Project.
+ */
+
+#ifndef GLX_EXT_INIT_H
+#define GLX_EXT_INIT_H
+
+/* this is separate due to sdksyms pulling in extinit.h */
+#ifdef GLXEXT
+extern void GlxExtensionInit(void);
+#endif
+
+#endif