Add stub visitor support for ir_texture.

ir_constant_expression.cpp

@@ -67,6 +67,7 @@ public:
    virtual void visit(ir_function_signature *);
    virtual void visit(ir_function *);
    virtual void visit(ir_expression *);
+   virtual void visit(ir_texture *);
    virtual void visit(ir_swizzle *);
    virtual void visit(ir_dereference_variable *);
    virtual void visit(ir_dereference_array *);
@@ -502,6 +503,15 @@ ir_constant_visitor::visit(ir_expression *ir)
 }
 
 
+void
+ir_constant_visitor::visit(ir_texture *ir)
+{
+   // FINISHME: Do stuff with texture lookups
+   (void) ir;
+   value = NULL;
+}
+
+
 void
 ir_constant_visitor::visit(ir_swizzle *ir)
 {