glsl: include stdio.h where needed

Acked-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: José Fonseca <jfonseca@vmware.com>

src/glsl/s_expression.cpp

@@ -24,6 +24,7 @@
 
 #include <assert.h>
 #include <limits>
+#include <stdio.h>
 #include "s_expression.h"
 
 s_symbol::s_symbol(const char *str, size_t n)

src/glsl/standalone_scaffolding.cpp

@@ -30,6 +30,7 @@
 #include "standalone_scaffolding.h"
 
 #include <assert.h>
+#include <stdio.h>
 #include <string.h>
 #include "util/ralloc.h"