Additionally pull up following revision(s) (requested by jakllsch in ticket #663):

external/bsd/ntp/lib/libntp/Makefile: revision 1.32
external/bsd/ntp/lib/libntp/Makefile: revision 1.33
external/bsd/ntp/lib/libntp/Makefile: revision 1.34

The substitute __DATE__ should be %b %e %Y per a C18 draft
Subtle change that won't make a functional difference in this case;
changed only for semantic correctness.

Increase MKREPRO robustness
- Use C locale to ensure month abbreviations are as expected
- bail out if MKREPRO_TIMESTAMP is not defined
- bail out if resulting __DATE__/__TIME__ replacement strings are empty

fix copy/paste-o

(martin)