Add openfloorrover and openceilingrover vars so that PIT_CheckLine can update tmfloorrover and tmceilingrover properly via P_LineOpening

...which should hopefully stop that issue where you just teleport back to the ground. Assuming this works as expected.

Also this is untested lol.

New CEZ scenery

See merge request STJr/SRB2Internal!257

Record Attack bg fixes

See merge request STJr/SRB2Internal!259

On second thoughts I'll go back to 8 for length in these variables, since as far as I can tell the code doesn't need it to be longer anyway

Fix crash with GME sounds when being freed

See merge request STJr/SRB2!504

Instead of ignoring blank menutypes in M_IterateMenuTree, ignore them in the MIT_ functions instead.

(I'm doing this because MIT_GetMenuAtLevel appears to actually care about whether menutype is zero or not unlike the others; I don't want to break the code designed around that)

Titlemap fixes

See merge request STJr/SRB2Internal!258

Slightly unrelated tweak: bghide && titlemapinaction clearly takes precedence over bgname if both are present, so reorder these if statement blocks

remove some of the GS_TIMEATTACK hacks I added because I now realise I can just turn titlemapinaction off when entering the menus \o/

* add gamestate != GS_TIMEATTACK checks to prevent Record Attack or NiGHTS Mode losing their backgrounds
* increase bgname to 9 to include the extra NULL byte? (is this a good idea actually)
* make M_IterateMenuTree ignore menu levels without a menutype value

The titlemap glitches turned out to be linked to deathmatchstarts, which wasn't actually properly cleared out each level load ...let's actually fix that, lol.

(Neither were the CTF starts but those didn't directly cause any problems luckily)

Improved libopenmpt loading

See merge request STJr/SRB2Internal!251

Fix wall spikes that start retracted

See merge request STJr/SRB2Internal!255

Thinkerlists fix

Closes #161

See merge request STJr/SRB2Internal!253

Unmute wood debris

See merge request STJr/SRB2Internal!254

I know this isn't my branch, but found several reference haemmoragers and figured it'd be appropriate to commit here.

Fixed the thinkerlist issues by removing THINK_LIMBO. Delay-removed thinkers now stay in their list.

Also includes toaster's assorted fixes and improvements from target_painted_on_your_ass.

Egg Colosseum (CEZ3 remaster)

See merge request STJr/SRB2Internal!248

Sea Egg

See merge request STJr/SRB2Internal!244

Fixed mixed-code-and-declaration, shadowed variables, etc ...and the compiler doesn't like P_AddEachTimeThinker being inline anymore for some reason, oh well