Add dependency so typingpool doesn't error out on `tp-assign`

[jonathanpberger]

Thanks to @imajes for finding and showing me how to fix this one.

[imajes]

I'm assuming here that-

a: portability across platforms isn't a problem here (not 1000% sure where fcntl is, but pretty sure it's not a problem for platforms people care about)

b: that given this wasn't required originally, and i can't find any easy google answer for whether ruby 1.8x automatically required it -- i'm assuming that @ryantate may have it wrapped into his ruby (OSX system ruby?) or something.

so, it should be safe... 👍