zasm and ed from ROM

SMS' RAM is much tighter than in the RC2014, which makes the idea of loading apps like zasm and ed in memory before using it a bit wasteful. In this recipe, we'll include zasm and ed code directly in the kernel and expose them as shell commands.

Moreover, we'll carve ourselves a little 1K memory map to put a filesystem in there. This will give us a nice little system that can edit small source files compile them and run them.