Fix DRI build

src/mesa/shader/prog_instruction.h

@@ -413,13 +413,12 @@ struct prog_instruction
     */
    GLint BranchTarget;
 
-#if 0
    /**
     * For TEX instructions in shaders, the sampler to use for the
     * texture lookup.
     */
    GLint Sampler;
-#endif
+
    const char *Comment;
 };