Adds 5 ambience maint tracks.

Yeah, credit goes to Cuboos.
The full track is here:
https://dl.dropboxusercontent.com/u/9654207/maint_amb_mixdown.wav
I cut it into five pieces of more or less 12 seconds long.

http://tgstation13.org/phpBB/viewtopic.php?f=9&t=1520

ALSO GODDAMNIT I MADE A PUNCTUATION MISTAKE IN MY COMMIT MESSAGE ;_;7