w_arc: various teleport/warp related fixes.

w_arc: various teleport/warp related fixes.

- Reset arc beam on warp/teleport.
- Lock arc beam for a RTT after reset (so the beam is straight at
  matching times/locations on client/server, after which everything is
  consistent again).
- Use unwarped view origin and angles on client to fix behaviour when
  the client is currently predicting the warp, as there's no signal for
  begin of warp prediction.
- Fix TrueAim-like logic on client when standing right against a wall
  (use the same avoid-shotorigin-poking-into-solid hack as other TrueAim
  code does).

warpzonelib: provide unwarped origin/angles in a variable.