* Again, tweak the spawning code to take maximum advantage of these gains.
* Fix potential crashes with MT_NULL mace/chain types supplied.
* #ifdef out the height-clipping code. It needs more TLC than I can give it right now, and the existing behaviour is less obviously broken (sadly enough).
* Fix chainmace points, which were apparently broken without anyone realising.
* Completely rework how mace/chainbars are spawned to reduce the number of matrix multiplications required EVEN FURTHER!
* Reimplement the maceretry solidity stuff (effect 4).
* Flip the mminlength stuff so that existing dev maps don't break badly.
* Fix hacky chainbar grabbing.
* Tweak height of tinychain a smidge.
* Fix ability to turn chains (still disabled by default, just at least want the option...)
* Replace max speed setting with a "minimum chainlink distance" setting - if greater than zero, that many chains will not be spawned from the center outwards. Doesn't affect the head of the chain at all, since otherwise what's the point? :V
* Handle all chain objects as a hnext/hprev chain.
* When removing mobjs with hnext/hprev, "repair the chain" (make the h links meet).
* Fix hidden slings, which I accidentially broke when I revamped maces the first time.
* Kill MF2_MACEROTATE. Not needed for anything anymore.
* P_MaceRotate now available to Lua to make up for it.
* Related: Made modifying hnext/hprev using Lua safer, so it keeps the reference counts in play.
Turns out compiling for Linux 32-bit using the Makefiles never actually defines LINUX! Apart from that, most of the existing Linux-specific code in SRB2's source code (except for tmap.s) actually uses __linux__ instead anyway
Additionally, place some optimisations in both software and OpenGL; in particular one has been added for when all of back and front sector (floor and ceiling) is sky: since everything is "open" anyway, we can simply the usual checks involved.
Thankfully it was really just a copy+paste of the code I already tinkered with for the normal ceiling sky based thok barriers, but tweaked for floors instead
(I suspect polyobject planes don't actually need the minx/maxx hacks anymore, but I haven't the time to test that tonight nor is this branch really suited for it anyway)
* Thok barriers with slopes now render fine in software
* The solid "sky walls" between different-height thok barriers adjacent to each other are gone. Forever.
This potentially allows FOFs and polyobjects to display sky flats on them properly, unless skyboxes are involved in which case they'd fail either way
I also updated or added comments to some places of the sky drawing code and related where useful
