mesa: consolidate PUBLIC macro definition

Define the macro in src/util/macros.h rather than in two different
places.  Note that USED isn't actually used anywhere at this time.

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

src/util/macros.h

@@ -156,4 +156,27 @@ do {                       \
 #   endif
 #endif
 
+/**
+ * PUBLIC/USED macros
+ *
+ * If we build the library with gcc's -fvisibility=hidden flag, we'll
+ * use the PUBLIC macro to mark functions that are to be exported.
+ *
+ * We also need to define a USED attribute, so the optimizer doesn't
+ * inline a static function that we later use in an alias. - ajax
+ */
+#ifndef PUBLIC
+#  if defined(__GNUC__) || (defined(__SUNPRO_C) && (__SUNPRO_C >= 0x590))
+#    define PUBLIC __attribute__((visibility("default")))
+#    define USED __attribute__((used))
+#  elif defined(_MSC_VER)
+#    define PUBLIC __declspec(dllexport)
+#    define USED
+#  else
+#    define PUBLIC
+#    define USED
+#  endif
+#endif
+
+
 #endif /* UTIL_MACROS_H */