Purge a bunch of legacy/unused stuff

See merge request STJr/SRB2!1801

Aren't used and definitely should not be in here anymore

Blast from the past, buuuut let's trim the fat here too.

Written in VB6. Superceded by better tools and also probably not even
buildable anymore.

SRB2 no longer works with 1.2 or Dreamcast so these are irrelevant

Superceded by far superior tools

Once more, SRB2 no longer works on DOS so this is irrelevant

SRB2 no longer works on DOS so this is irrelevant

Also unsupported and nonfunctional

This thing is ancient history and also depends on FMOD.

cmake: Various macOS build/package improvements

See merge request STJr/SRB2!1800

yay icon

This properly links dylibs set during build instead of expecting
the libraries to be in the system path.

UDMF conversion: Fix noclimb flag not being applied to linedef types 66-68

Closes #868

See merge request STJr/SRB2!1790

Fix copypaste error in P_GetMobjGravity

Closes #867

See merge request STJr/SRB2!1791

Update triggertag on sector tag fset

Closes #865

See merge request STJr/SRB2!1789

Change UDMF wall scroll scale to SCROLL_SHIFT

Closes #862

See merge request STJr/SRB2!1788

UDMF special 502 now must scale arg 2 and 3 in the same scale
space as line length scrolling in binary format. This
is to ensure compatibility with the binary format.

Fixes STJr/SRB2#862

Co-Authored-By: MascaraSnake <jonassauer27@gmail.com>

Fixes STJr/SRB2#865

UDMF: Linedef executors

See merge request STJr/SRB2!1625

UDMF: The whole thing

See merge request STJr/SRB2!1714

# Conflicts:
#	extras/conf/udb/Includes/SRB222_things.cfg

# Conflicts:
#	src/p_mobj.c
#	src/p_spec.c

# Conflicts:
#	src/p_spec.c