* The existing structs are now exclusively for handling extra data.
* `specialStage` has been renamed to `specialstageinfo`, to reflect that it is not the sole arbiter.
* `specialstageinfo.valid` and `bossinfo.valid` are what must be checked before grabbing data from either struct.
* These are turned on when the gametype extra data is successfully initialised, not on map start.
* `K_InitBossHealthBar(...)` for `bossinfo.valid`
* `K_InitSpecialStage(void)` for `specialstageinfo.valid`
* `K_CanChangeRules(...)` no longer checks these
* No longer uses duplicate encore information.
* The map command (and -warp) now guesses gametype using a general `G_GuessGametypeByTOL(UINT32)` function
* Grabs the first gametype with an overlap between the requested TOL and the gametype's TOL.
* The cool Versus-specific intro is now checked via `K_CheckBossIntro()`.
* Actually add descriptions for the boss-related functions into k_boss.h.
* Introduce K_ResetBossInfo, an internal-only function for handling situations where it needs to be cleared.
* Fix a bug where bossinfo wasn't reset when using the map command to go to a battle map after having been in a boss.
* Fix some bugs where you could provide magnitudes out of the desired range to K_InitBossHealthBar and K_UpdateBossHealthBar.
