SkinTunes: Per-Racer Tune.Song Swapping Defined By S_SKIN Data

ringracers_user-defined-skintunes_cTRR1W3Q1v

For every racer WAD in the game, mod developers may now optionally specify a variety of new key-value pairs in the S_SKIN lumps for said racer to personalize "event" Tunes to the design of the racer so long as the Tune in question has its name specified in the global array skins_skintunenames. The existence of skins_skintunenames is by-design to filter what Tunes are and are not allowed to be altered by this MR for artistic purposes.

When an aforementioned key-value pair is specified, the key represents the Tune that will be interacted with (prefixed by MUS) and the value represents the loaded OGG lump for the .song it will play instead of the usual .song. Whilst the intent is to let racers use their own custom OGG lumps, existing loaded OGG lumps work all the same. Interaction with any Tune involved prior to this MR will remain unaffected as the .song adjusted is actually on a deep copy of affected Tune instances cached in-advance during Music_Init().

Expanding the system to include more tunes is specifically engineered to be as easy as adding a new tune name to skins_skintunenames. After doing so, S_SKIN will gain access to replacing the .song of that Tune at runtime (so long as the Tune added to skins_skintunenames was present during Music_Init() at least at the time of submitting this MR).

As I submit this MR prior to any editing that may occur, skins_skintunenames only has 2 entries:

char skins_skintunenames[NUMSKINTUNES][MAXSKINTUNENAMELEN + 1] = {
	"invinc",
	"grow"
};

Although heavily implied already, I will directly state now that any existing racers are 100% un affected by this MR, no assets will need to update to accommodate it.

This MR went through several iterations and at first was a little out of my scope in terms of my understanding of the codebase, so hopefully it is acceptable even so!

As for the future of the MR, I'm willing to expand the scope into engineering a solution for things like the sound effect versions of the invinc and grow music used as a warning to nearby racers but I also feel that starts to drift from the goal of this MR as an all-purpose solution to per-skin Tune manipulation and may want to take an idea like that into a sibling MR.