glx: Disable indirect GLX contexts by default.

Almost every situation of someone running indirect GLX is a mistake
that results in X Server crashes.  Indirect GLX is the cause of
regular security vulnerabilities, and rarely provides any capability
to the user.  Just disable it unless someone wants to enable it for
their special use case (using +iglx on the command line).
Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Keith Packard <keithp@keithp.com>
Signed-off-by: Keith Packard <keithp@keithp.com>

os/utils.c

@@ -194,7 +194,7 @@ Bool noGEExtension = FALSE;
 
 Bool CoreDump;
 
-Bool enableIndirectGLX = TRUE;
+Bool enableIndirectGLX = FALSE;
 
 #ifdef PANORAMIX
 Bool PanoramiXExtensionDisabledHack = FALSE;