clean player name before using it in filename.  prevents weird cases when
saving files with (possibly invalid) utf-8 sequences in them.  also strips
color codes because they render oddly on commandline.
also strip out ascii chars windows cannot handle in filenames.
use null instead of empty string
Merge pull request #509 from dpadgett/svdemo

[MP] svdemo: clean player name before using it in filename.  prevents weird cases whe...
[JK2SP] JK2 writes USERINFO cvars to saves, we write both in jk2 mode for now.
[JK2SP] Assign correct hudfiles in ui module for jk2mode.
[JK2SP] Merging in some fixes and cleanup from JASP cgame/game code.
[JK2SP] Hopefully fixing timer save/load code by using a modified version of JA's code, but keep compat with JO.
This commit should remove the requirement for std c++11 requirement in master branch.
Refs #498.
[JK2SP] Fix source group of jk2 sp's "game" folder files.
[JK2SP] Whoops force_sight doesn't exist.
[JK2SP] Added missing flash radius fix to JK2.
[SP] Fix dlights when in jk2 mode.
[SP] Clean up the usage for save cmd.
[SP] Savegame related prints now show up correctly under JK2 mode.
[SP] Remove unused ui_hide*callout cvars.
[SP] Don't try to draw splash in JK2 Mode.
[JK2SP] Whoops, remove force seeing check since it does not exist.
[JK2SP] There's only 9 crosshair images.
[JK2SP] Fix menu parse message print spacing.
[SP] Fix SV_AdjustAreaPortalState when building JK2 exe.
Fixes #511

Looks like there was incorrect removal of com_jk2 here.