Support for 32 bit protected mode DOS

This patch adds support for compiling a 32 bit protected mode version of frotz using djgpp.

The 16 bit version is still useful especially if you want to run it on a system that predates the 386, but if you are running it under dosbox or on a 386 or later I think having a 32 bit version of the interpreter is better. So I went and creted this port for djgpp.

This adds a new target to the main makefile called "djgpp" that can be used compile frotz32.exe under the cross compiling djgpp toolset. This should also help with memory issues since this version is no longer limited to 640k of memory.

I also reworked the sound blaster code in this one, to remove some limitiations of the old version. In particular it supports playback of audio files more then 64k in size, and also stereo on the pro and sound blaster 16. As well as doing 16 bt playback on the sound blaster 16.

While graphics are still loaded from files on the disk, this version does now load audio from blorb files (only AIFF support) now.