First phase of TLS work. At this point SPARC assembly dispatch is

broken, but it will be fixed "shortly."  This is pretty much the same
as the patch I sent to the dri-devel list on 22-Jun-2004.

src/mesa/drivers/dri/common/dri_util.c

@@ -54,6 +54,14 @@
 typedef GLboolean ( * PFNGLXGETMSCRATEOMLPROC) (__DRInativeDisplay *dpy, __DRIid drawable, int32_t *numerator, int32_t *denominator);
 #endif
 
+/**
+ * Weak thread-safety dispatch pointer.  Older versions of libGL will not have
+ * this symbol, so a "weak" version is included here so that the driver will
+ * dynamically link properly.  The value is set to \c NULL.  This forces the
+ * driver to fall back to the old dispatch interface.
+ */
+struct _glapi_table *_glapi_DispatchTSD __attribute__((weak)) = NULL;
+
 /**
  * This is used in a couple of places that call \c driCreateNewDrawable.
  */