Increase maximum number of material-texture combinations to 255

This is the maximum we can do. One value is reserved for diff / transparency,
and we have 8bpp surfaces.

src/config/C4Constants.h

@@ -49,7 +49,7 @@ const int
 const int 
 	C4M_MaxName = 15,
 	C4M_MaxDefName = 2*C4M_MaxName+1,
-	C4M_MaxTexIndex = 127; // last texture map index is reserved for diff
+	C4M_MaxTexIndex = 255; // last texture map index is reserved for diff
 
 const int C4S_MaxPlayer = 4;