new perf test in pat.t: avoid timing failure

new perf test in pat.t: avoid timing failure

A new performance test in re/pat.t added by v5.23.9-58-gd14d585 could
occasionally fails to a timing issue. It was checking that the the
test took less than 1 sec to run; but since the clock usually has a
granularity of 1 sec, it could fail if the test ran over a tick boundary.

Change the condition to <= 1 sec, and increase the time the test takes on
a bad perl - it was taking 4sec on my system; it now takes about 14sec,
so there's less chance of a bad perl passing.