Add original checkbashisms.pl #30

http://anonscm.debian.org/cgit/collab-maint/devscripts.git/commit/scripts/checkbashisms.pl?id=68e6970dd7a536a736270075a655d30633ca9022
$ wget http://anonscm.debian.org/cgit/collab-maint/devscripts.git/plain/scripts/checkbashisms.pl
Switch checkbashisms rule to accept jobs command #30

POSIX2_UPE must be supported to execute shoreman.
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap02.html#tag_02_01_03_02
Execute fixed checkbashisms.pl #30