checkincludes: fix perlcritic warnings

Turn on strict checking.
Use local file handles.
Use three argument open.

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