OSX: implement AGSMac::GetUserGlobalConfigDirectory()

This routes global ags config to "Library/Application Support/uk.co.adventuregamestudio/",
I believe this is where it was supposed to be located.

Engine/platform/osx/acplmac.cpp

@@ -47,6 +47,7 @@ struct AGSMac : AGSPlatformDriver {
   FSLocation GetUserSavedgamesDirectory() override;
   FSLocation GetAllUsersDataDirectory() override;
   FSLocation GetUserConfigDirectory() override;
+  FSLocation GetUserGlobalConfigDirectory() override;
   FSLocation GetAppOutputDirectory() override;
   const char *GetIllegalFileChars() override;
 };
@@ -103,6 +104,11 @@ FSLocation AGSMac::GetUserConfigDirectory()
   return FSLocation(libraryApplicationSupport);
 }
 
+FSLocation AGSMac::GetUserGlobalConfigDirectory()
+{
+  return commonDataPath;
+}
+
 FSLocation AGSMac::GetAppOutputDirectory()
 {
   return commonDataPath;