Handle signals correctly on linux

See merge request STJr/SRB2!530

Flats in walls

See merge request STJr/SRB2!548

Better Deadzones

See merge request STJr/SRB2!541

Choose a random port as a client

See merge request STJr/SRB2!554

This reverts commit 2a9a2c0f.

If you ever need to, you can change the client port number.

Using strcpy is stupid because we don't know how long the argument would be.
There's no need for a buffer anyway.

Let the map command warp to maps without a level header

See merge request STJr/SRB2!528

Various cmake adjustments

See merge request STJr/SRB2!538

Don't be mean to Tails plz (Pandora's Box Super cheat fix)

See merge request STJr/SRB2!540

Despite popular belief, this was just some experimenting from 2.2 development that we forgot to remove!

Add menu items for deadzone.

Additionally fixes some weird padscale 0 stuff that was flipped.
This does have gameplay implications in both NiGHTS and regular gameplay. Notably you won't feel like you're locked into up/down left/right when you want to turn, but this can make running perfectly straight a little bit more tricky.

Tilted ripple

See merge request STJr/SRB2!524

OpenGL fixes

See merge request STJr/SRB2!519

Restore portal culling code that went gone by pure accident

See merge request STJr/SRB2!523

Optimize Software drawers

See merge request STJr/SRB2!533

Add TC_DASHMODE color shader

See merge request STJr/SRB2!526

Fix Ploadflat closing the game with "Too many flats in level" error message

See merge request STJr/SRB2!529