[Ohrrpgce] SVN: teeemcee/8472 Fix Game not deleting g_debug.txt when running under Custom

[subversion at HamsterRepublic.com]

teeemcee
2017-02-28 07:15:23 -0800 (Tue, 28 Feb 2017)
335
Fix Game not deleting g_debug.txt when running under Custom

This resulted in messages like
fileisreadable: Error 1 reading /mnt/common/ohrrpgce/spare-git/g_debug.txt

The cause was inworkingdir returning NO, which translated to
FilterActionEnum.DENY

Also added new (unused) HIDE filter action, and add FB error constants to
fb_stub.h
---
U   wip/fb/fb_stub.h
U   wip/filelayer.cpp
U   wip/filelayer.h
U   wip/lumpfile.bas
U   wip/lumpfile.bi