Added version 7.3* for Apple's clang compiler

Author: agbaroni

configure

@@ -1034,7 +1034,7 @@ then
         if [ -n "$CFG_OSX_CLANG_VERSION" ]
         then
             case $CFG_OSX_CLANG_VERSION in
-                (7.0* | 7.1* | 7.2*)
+                (7.0* | 7.1* | 7.2* | 7.3*)
                 step_msg "found ok version of APPLE CLANG: $CFG_OSX_CLANG_VERSION"
                 ;;
                 (*)