patchbomb: normalize date format in generated mboxes
mbox format should use time.asctime(). Unfortunately, this function writes
2-characters day of week on Windows while unix one writes a single character.
Normalize to Windows version since the other one can hardly be written with
strftime().
adding base
foo/renamed
renamed
bar/renamed
renamed
baz
.hg/patches/baz
% test patch being renamed before committed