checkversion: perl cleanup

Turn on strict checking.
Use three arguement open
Standard practice in perl is to use undef not zero for false

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Cc: Cong Wang <amwang@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Michal Marek <mmarek@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Michal Marek <mmarek@suse.cz>