Explicitly turn off negative epoch testing on VMS. Change #24310 from bleadperl, Craig Berry.
In the test suite when checking on whether negative epochs are allowed, use 3 days before the epoch as a test, because just one hour before may give false positives (for example on Win32 with the Borland compiler).
Reverted an earlier change that slightly extended the range of values for which timelocal worked (by about a day in either direction) because it could cause an incorrect answer for certain epoch values on the date of a DST change. Reported by Gisle Aas.