* Actively impede your acceleration
* Make your animation speeds faster whenever you're moving (to give off that Looney Tunes effect)
The former change is something that was present in the few low-friction circumstances in the classics, and makes low-friction surfaces more of an active challenge. The latter change is just something I did for fun to more clearly communicate that things are different with the physics here.
High friction surfaces DO NOT involve any of this, since it ended up basically cheesing their existing gameplay.
*Friction linedef effect is now -
1) controlled by x offset instead of length - offset of -100 is maximum iciness, offset of +483(!!!) is the maximum sludginess BUT things are scaled such that +100 is about the maximum sludginess any reasonable human being would want in a level, 0 is ORIG_FRICTION)
2) not reliant on a sector special to function (can be applied solely by tag to in-map sectors or solid FOF control sectors)
* -lSDL2_mixer is already added to SDL_LDFLAGS by default, unless NOMIXER=1 is set
* -DSDLMAIN should also be added to OPTS by default for MINGW=1 builds, unless NOSDLMAIN=1 is set
NiGHTS hotfix
Fixes the following issues relating to playing as NiGHTS Super Sonic that apparently popped up between 2.1.14 and next (mostly due to the changes to SRB2's trig stuff it seems):
* Super Sonic drifts to the side at some angles around an axis, and is unable to go directly upwards or downwards as a result
* Drilling to the side when on the ground causes the drill sound to constantly restart
* CEZS's start not actually being lined up properly with the first axis means the player is not able to go backwards along the track (because the player is not actually aligned with the track properly, preventing you from touching the attached line transfer)
* trying to hug some walls such as the tall wall before the library section of CEZS allows Super Sonic to go through them
These fixes needs proper testing before this branch can be merged in, in case they accidentally break other things as a result or something.
See merge request !71
Basically I kind of worked around any potential trig inaccuracies by not using the player position directly for setting momx/momy. This way, if player->angle_pos == player->old_angle_pos, momx/momy are zero
