Avoid dsusp on BSD variants like OSX
Avoid dsusp on BSD variants like OSX

This was making Control-Y background the jline process, then crash on
foregrounding it.

refs #94

renew-tgi/jline2,msaxena2/jline2,DALDEI/jline2,scala/scala-jline,kaulkie/jline2,scala/scala-jline,fantasy86/jline2,ctubbsii/jline2,tkruse/jline2