make __CONCAT portable

Upstream: Yes, https://github.com/intel/intel-graphics-compiler/pull/138
---
--- a/inc/common/UFO/portable_compiler.h
+++ b/inc/common/UFO/portable_compiler.h
@@ -125,9 +125,10 @@
 /* compile-time ASSERT */
 
 #ifndef C_ASSERT
-    #define __UNIQUENAME( a1, a2 )  __CONCAT( a1, a2 )
-    #define UNIQUENAME( __text )    __UNIQUENAME( __text, __COUNTER__ )
+    #define __CONCATING( a1, a2 )     a1 ## a2
+    #define __UNIQUENAME( a1, a2 )  __CONCATING( a1, a2 )
 
+    #define UNIQUENAME( __text )    __UNIQUENAME( __text, __COUNTER__ )
 
     #define C_ASSERT(e) typedef char UNIQUENAME(STATIC_ASSERT_)[(e)?1:-1]
 #endif