Avoid warnings for Xopen 7.00 and higher (see #364)

src/civetweb.c

@@ -127,6 +127,12 @@ mg_static_assert(sizeof(void *) >= sizeof(int), "data type size check");
 
 #ifdef __MACH__
 
+#ifdef __clang__
+/* Avoid warnings for Xopen 7.00 and higher */
+#pragma clang diagnostic ignored "-Wno-reserved-id-macro"
+#pragma clang diagnostic ignored "-Wno-keyword-macro"
+#endif
+
 #define CLOCK_MONOTONIC (1)
 #define CLOCK_REALTIME (2)