Autobrake polish

Closes #176

See merge request STJr/SRB2Internal!293

P_PlayerCanDamage fix

See merge request STJr/SRB2Internal!291

# Conflicts:
#	src/d_netfil.c

Compare the file name only for real

See merge request !511

Calling all Lua consvars

See merge request !509

CL_SendRequestFile prepends the path for each file.

GFZ boss rework + boss explosion fun

See merge request STJr/SRB2Internal!290

* Make it actually look like a brake, so people can tell it's on instead of just having high friction.
* Fix it fucking with spring chains (caused by being unwittingly active for the first tic of spring collision).

Added quick validity checks for three linedef executor specials that require a player mobj to be the triggerer (432, 434 and 437)

* Make sure the consvar's properties are all initialised to zeros as defaults
* Error if the consvar is not given a name
* Error if the consvar has CV_CALL but no call function
* Error if the consvar has CV_NOINIT but not CV_CALL

MI cleanup returns

See merge request STJr/SRB2Internal!292

Fix all our landing woes. (For now.)

See merge request STJr/SRB2Internal!289

# Conflicts:
#	src/config.h.in
#	src/d_clisrv.c
#	src/d_netcmd.c
#	src/doomdef.h
#	src/p_map.c
#	src/p_maputl.c
#	src/sdl12/macosx/Srb2mac.xcodeproj/project.pbxproj

Update version to 2.1.25

See merge request STJr/SRB2!507

Fix an exploit where players could steal the final hash of a login

See merge request STJr/SRB2!508

PolyObject crush hotfix

See merge request !506

Use P_MobjInsidePolyobj instead of P_MobjTouchingPolyobj, so that you can be crushed by the polyobject's middle rather than just its edges

PolyObject fixes backport

See merge request !505

# Conflicts:
#	src/p_user.c

After looking at the FOF part of P_LineOpening for a while I now realise many of these variables aren't even necessary, so I removed them all.

(Naturally I did the same to the camera equivalent)

# Conflicts:
#	src/p_maputl.c