glx: Move initialization of ext_list_first_time to where it's storage is allocated

Move the initialization of ext_list_first_time from all of the DRI loader's
CreateScreen routines, to where the storage for the screen config is
allocated.

It needs to get set in the screen-config even if DRI is forced off
using LIBGL_ALWAYS_INDIRECT, so that psc->direct_support is initialized
correctly, otherwise __glXExtensionBitIsEnabled() always returns FALSE

Specifically, this causes a problem with an X server which advertises
GLX<=1.2, and the GLX_SGIX_fbconfig extension.
glXGetFBConfigFromVisualSGIX() uses __glXExtensionBitIsEnabled() to
check if the GLX_SGIX_fbconfig extension is available, but that function
won't return correct information because that data has never been
initialized, because ext_list_first_time was never set...

Signed-off-by: Jon TURNEY <jon.turney@dronecode.org.uk>
Signed-off-by: Brian Paul <brianp@vmware.com>

(cherry picked from commit 96ab4d2b84)

src/glx/dri2_glx.c

@@ -519,9 +519,6 @@ dri2CreateScreen(__GLXscreenConfigs * psc, int screen,
    if (psp == NULL)
       return NULL;
 
-   /* Initialize per screen dynamic client GLX extensions */
-   psc->ext_list_first_time = GL_TRUE;
-
    if (!DRI2Connect(psc->dpy, RootWindow(psc->dpy, screen),
 		    &driverName, &deviceName)) {
       XFree(psp);