Fix string-quoting checks. Was breaking team joining etc.

Unfortunately, our code has a mix of (source, dest[, length]) and (dest[,
length], source) in function prototypes. We need to fix this, or this kind
of problem is likely to occur again. My preference is for the latter, giving
consistency with the likes of the standard C library: least surprise and all
that.
Add two missing buffer validation checks for string quoting.
Add VisTest functions to check if a 3D-point is visible in the current view
and use it to implement light flare entities.

The old trace-based code used the bounding box instead of the actual model
to cull flares.
Use the position provided in the path corridor to calculate steer direction
Only set lastRouteTime after we have found start/end polys
Make the caller specify the extents when finding a navmesh poly
Change g_tag from gpp to unv
Adjust help text to somewhat better reflect current Unvanquished.

This text still needs a rewrite.
Port TTY client from TremFusion
Fix tty client
Add togglemenu command.
Make UI_CVAR_CREATE use VM specific code

Makes cvar be flagged as VM created and unset ROM if ARCHIVE is set.
Fix MSG_ReadDeltaKey setting bit 1<<bits often

MSG_ReadDeltaKey would often set 1<<bits, it should never be set. It exceeds the size of what was being read.
Worked okay for weapons/forward/right/up as they stored as chars (value would wrap around to correct value, lucky).
Angles had the wrong value, not sure if it was causing issues.
Remove MSG_WriteDeltaUsercmd and MSG_ReadDeltaUsercmd
Fix resolving IPv6 favorites in Team Arena UI
5717 - Gamecode can open file "" for reading
On Windows, add \r\n to each line of the console dump.
5097 - Menu corrupted on start (on IRIX)

(Unvanquished/dsalt: GL_ACCUM_BUFFER_BIT removed from the glClear() calls.
We don't use any accumulation buffers.)
Stop legs/torso bone count mismatch from causing disconnection.

The problem only occurs, so far as I can tell, when switching between
players on the human team when spectating when the formerly-spectated
player is represented using an MD3 model and the newly-spectated player is
represented using an MD5 model.

This will cause short-term rendering glitches and console spam; but better
that than disconnection.
Mark bones mismatch message as skipnotify; add \n.