Use C-style system headers in C++ code to avoid issues with std:: namespace

src/glsl/lower_mat_op_to_vec.cpp

@@ -35,9 +35,6 @@
 #include "ir_expression_flattening.h"
 #include "glsl_types.h"
 
-using std::abort;
-using std::printf;
-
 class ir_mat_op_to_vec_visitor : public ir_hierarchical_visitor {
 public:
    ir_mat_op_to_vec_visitor()