Patch from Sven Eden via bug 552370
https://bugs.gentoo.org/show_bug.cgi?id=552370

--- a/include/IL/il.h	2009-03-08 08:10:08.000000000 +0100
+++ b/include/IL/il.h	2015-09-03 16:22:04.056637044 +0200
@@ -63,13 +63,13 @@
 	#endif
 #endif
 
-#ifdef RESTRICT_KEYWORD
-#define RESTRICT restrict
-#define CONST_RESTRICT const restrict
+#if defined(RESTRICT_KEYWORD) && !defined(__cplusplus)
+#define RESTRICT __restrict__
+#define CONST_RESTRICT const __restrict__
 #else
 #define RESTRICT
 #define CONST_RESTRICT const
-#endif
+#endif // RESTRICT keyword and not C++
 
 #include <stdio.h>