generate_dungeon.c: generates a dungeon map

Compile: `make`
Run: `./generate_dungeon <optional seed>`

Prints the dungeon map along with the seed that created it.
If a seed is specified, it is used for the generator,
otherwise a random seed is picked.

Maps have 6-12 connected rooms, (4-10) by (3-8) map cells size.
Each map has one or two staircases of each type.