Fix the strftime text for HPUX

Expunge one of the conversion specifications passed to strftime(3) for
HPUX only. The %F spec in common libc implementations is equivalent to
'%Y-%m-%d', whereas on HPUX it's something entirely different, expanding
to the locale-specific full month name (i.e. March).
MAC mode of sort() broken on HPUX, see #4934
Mark as broken on HPUX instead of sanitizing: issue #4940
Merge pull request #1574 from aappilattoq/master

hpux: strftime, sort