Auto merge of #494 - johalun:dragonfly-ttycom, r=alexcrichton
Auto merge of #494 - johalun:dragonfly-ttycom, r=alexcrichton

Added some DragonFly-only ttycom.h constants.

I overlooked some DragonFly-only constants in the last PR.

superriva/libc,philippkeller/libc,anatol/libc,cactorium/libc,rust-lang-nursery/libc,rust-lang/libc,rust-lang-nursery/libc,anatol/libc,mneumann/libc,mneumann/libc,rust-lang-nursery/libc,superriva/libc,mneumann/libc,cactorium/libc,rust-lang/libc,anatol/libc,philippkeller/libc,superriva/libc,rust-lang/libc,cactorium/libc,philippkeller/libc