0.9.18.15: fix adjust-array :fill-pointer buglet, plus housekeeping

0.9.18.15: fix adjust-array :fill-pointer buglet, plus housekeeping
 * Reported by Lars Brinkhoff: "An error of type error is signaled if
   fill-pointer is supplied and non-nil but array has no fill pointer."
 * Test-case.
 * Improve the localtime/gmtime KLUDGE for Windows: instead of
   flipping the sign of time, use zero -- still arbitrary, but
   slightly less so. "Where there timezones before 1970, geez!"
 * Oops! Broken test-case from 0.9.18.12 fixed.