spearmint: OpenGL2: Fix setting (unused) dlightBits

If num_dlights is 32, the dlightBits were set to 0. Now it's correctly set
to UINT_MAX. However the "tr.refdef.dlightBits" variable isn't actually used
for anything in the OpenGL2 renderer.

Fixes undefined behavior reported by cppcheck analyzer.

code/renderergl2/tr_light.c

@@ -72,7 +72,7 @@ void R_CullDlights( void ) {
 		tr.refdef.num_dlights = MAX_DLIGHTS;
 	}
 
-	tr.refdef.dlightBits = ( 1 << tr.refdef.num_dlights ) - 1;
+	tr.refdef.dlightBits = ( 1ULL << tr.refdef.num_dlights ) - 1;
 #else
 	int i, numDlights, dlightBits;
 	dlight_t    *dl;