Fix various buffer overruns parsing pad UI
Fix potential null dereference parsing UI pad
Move d_fname helper methods to base class ntstring
Fix crash loading descent.cfg with bare equal

Remove obsolete check for trailing newlines in strings.  Fix failure to
null terminate strings.  Refuse overlong strings.  Refuse integers with
trailing garbage.  Refuse integers out of range.
Reset Current_level_name where needed
Fix buffer overrun reading UI pad
Fix crash choosing jukebox directory

newmenu_listbox1 returns immediately
Use ntstring for CMLevelMusicPath
Use array<ntstring> for CMMiscMusic
Fix crash loading player.ngp with bare equal
Use ntstring for UI_KEYPAD description
Hide marker _ when buffer full
Use ntstring for Netgame.game_name
Use ntstring for Netgame.mission_name
Use ntstring for mission_name
Move wall declarations to fwdwall.h
Reduce inclusion of wall.h
Move segment declarations to fwdsegment.h
Pass physics_set_rotvel_and_saturate arg by &
Fix polyobj for WORDS_NEED_ALIGNMENT