Move UNUSED out of C++11-dependent #ifdef

Author: hostilefork

src/portab.h

@@ -52,13 +52,15 @@
 #endif
 
 
-// In C++11 UNUSED(x) is explicitly provided
+// http://stackoverflow.com/a/4030983/211160
+// Use to indicate a variable is being intentionally not referred to (which
+// usually generates a compiler warning)
+#ifndef UNUSED
+#define UNUSED(x) ((void)(true ? 0 : ((x), void(), 0)))
+#endif
+
+
 #if __cplusplus <= 199711L
-  #if defined (_MSC_VER)
-    #define UNUSED(x) (void) (x);
-  #else
-    #define UNUSED(x) (void) (sizeof((x), 0))
-  #endif
   #ifndef __clang__
      #define nullptr NULL
   #endif