glsl: fix compile errors with mingw due to missing PRIx64 definitions

define __STDC_FORMAT_MACROS and include <inttypes.h> (same as
ir_builder_print_visitor.cpp already does).

Otherwise, some mingw build errors out (since
8e7e1ae036 and
bbce1c538d presumably) with:
src/compiler/glsl/ir_print_visitor.cpp:479:40: error: expected ‘)’ before ‘PRIu64’
   case GLSL_TYPE_UINT64:fprintf(f, "%" PRIu64, ir->value.u64[i]); break;

(Note even with that fix I get other format specifier warnings:
src/compiler/glsl/ir_print_visitor.cpp:473:47:
warning: unknown conversion type character ‘a’ in format [-Wformat=]
                fprintf(f, "%a", ir->value.f[i]);
                                               ^
src/compiler/glsl/ir_print_visitor.cpp:473:47:
warning: too many arguments for format [-Wformat-extra-args]
but it still compiles at least)

Reviewed-by: Jose Fonseca <jfonseca@vmware.com>

src/compiler/glsl/ir_print_visitor.cpp

@@ -21,6 +21,8 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#define __STDC_FORMAT_MACROS 1
+#include <inttypes.h> /* for PRIx64 macro */
 #include "ir_print_visitor.h"
 #include "compiler/glsl_types.h"
 #include "glsl_parser_extras.h"