Unprediction needs to restore selected inventory
Remove disconnecting players safely

Players who were disconnecting would be removed outside of the playsims
control, causing problems with sector lists.
Remove PacketServer auto select

PacketServer has the tendency to amplify netgame latency times, so it
really shouldn't be auto selected.
Added a notice in case it's used.
Unreliable isn't exactly the problem
Keep gateway sockets open during handshake
Started work on prediction lerping
Further work on prediction lerping
Final work on prediction lerping

Added cl_predict_lerpscale and cl_predict_lerpthreshold
Added options in menudef
Made sure that lerping cannot extrapolate or run on small scales
Lerping gets reset when rendering interpolation does or respawn
Moved prediction lerp reset to cover all cases.
Prevent lerping when tic duplication not 1

Network dup makes player prediction inaccurate
- Removed unnecessary 'id' variable from AActor.
- Removed unused 'backpack' variable from player_t.
- Removed duplicate code from b_move.cpp.
- General cleanup.
Merge branch 'multi' of https://github.com/Edward850/zdoom