DOOM 'Marine's Best Friend' with Sigil support

This is MBF modified to accomodate Sigil & Sigil II as proper 5th and 6th episodes. I got the source code from here and ported the changes from libretro-prboom (pull requests 88 to 90 and 97)

Compiling

Pre-requisites

• allegro 3.0
• an old djgpp version from MBF's era (confirmed working: bnu27b.zip, djdev201.zip, GCC2721B.ZIP, mak3791b.zip, txi390b.zip)
• a pc running dos (dosbox is fine too)

Steps (on Linux with dosbox installed)

• Clone this repo
• Unzip djgpp into a new folder in your checkout called djgpp such that gcc is at djgpp/djgpp/bin/gcc.exe
• Unzip the allegro 3.0 sources to a new folder in your checkout called allegro
• Run ./build.sh allegro which will run dosbox for you with the right settings (current folder mounted as c:\) and build allegro.
• Then you can ./build.sh mbf to build MBF.

Changes

• Added full support for episode 6: Sigil II
• Added full support for episode 5: Sigil.
• Sound card settings are read from allegro.cfg again.

Important notes

• You need to use The Ultimate Doom wad (named DOOM.WAD or DOOMU.WAD).
• SIGIL_SHREDS.WAD is not supported for obvious reasons (no mp3 playback).
• To play Sigil II, you need to also load Sigil (-iwad doom.wad -file sigil.wad -file sigil2.wad).