tests: remove a non portable localtime test

tests: remove a non portable localtime test

* tests/misc/date.pl: This test was dependent on perl
unconditionally calling the system localtime() as date(1) does.
However perl has its own configure checks in place to avoid buggy
localtime implementations.  Therefore comment out this test
as a FIXME for now.  This test was seen to fail on FreeBSD 10
where localtime() returns nonsense values instead of failing
for arguments >= 2^56.