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

src/glsl/ast_expr.cpp

@@ -20,12 +20,9 @@
  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  * DEALINGS IN THE SOFTWARE.
  */
-#include <cstdio>
-#include <cassert>
+#include <assert.h>
 #include "ast.h"
 
-using std::printf;
-
 const char *
 ast_expression::operator_string(enum ast_operators op)
 {