r300: Workaround problem on R500 with very large fragment programs

The non-KMS interface is to blame here. In theory, a proper fix
could be produced that works for the KMS interface only, but it
require cleaning a lot of mess. Easier to just do it right in r300g.

Signed-off-by: Nicolai Hähnle <nhaehnle@gmail.com>

docs/relnotes-7.6.1.html

@@ -41,6 +41,7 @@ tbd
 <li>glXQueryContext(GLX_RENDER_TYPE) returned wrong values (bug 24211)
 <li>GLSL sqrt(0) returned unpredictable results
 <li>Fixed default texture binding bug when a bound texture was deleted.
+<li>r300: Work around an issue with very large fragment programs on R500.
 </ul>
 
 </body>