This fixes up the *BSD handling within the Operating System check.
SYS is now set to the OS without the version attached as provided
by ${host_os} (.e.g. openbsd instead of openbsd5.1) to match all
the other OS's and simplifies other OS's checks further down. This
also allows the script to recognize DragonFly.

This is back porting 4bee377fec3a95fe6681b0af3517f38064c336f2 to 2.0.

There was a typo with the initial patch.
Signed-off-by: Rémi Denis-Courmont <remi@remlab.net>