* include/freetype/internal/ftgloadr.h: Add missing header.

Noticed by Jouk Jansen.
diff --git a/include/freetype/internal/ftgloadr.h b/include/freetype/internal/ftgloadr.h
index 76ed573..fea931c 100644
--- a/include/freetype/internal/ftgloadr.h
+++ b/include/freetype/internal/ftgloadr.h
@@ -22,6 +22,7 @@
 
 #include <freetype/freetype.h>
 
+#include "compiler-macros.h"
 
 FT_BEGIN_HEADER