MacOS GUI module needs purge of obsolete --server-port code

The --server-code option was made obsolete during development of v2.0.

Yet, the modules/gui/macosx/windows/VLCOpenWindowController.m code still tries to read the value of this "server-port" option in six places.

I'm not familiar enough with this MacOS code to be best placed to properly address this currently. (Nor do I have a Mac to test with).

I believe that these config_GetInt("server-port") calls are currently always returning 0 (I believe the call would find the option, and that the value field would always be 0 for obsolete options; I used to know the details better, but that's what seems to be the case taking a quick look now).

In !119 (merged) I've skipped over purging this option in order to not break the existing behaviour here (would cause a -1 value to be returned instead of 0). Perhaps when this is fixed, the old obsolete option can then be removed also.