MFC r305265:

Revert r304192 to fix short month names and replace %b with %_m in date_fmt
for Chinese locales.

As mentioned in the commit message of r289041, nl_langinfo(ABMON_*) only
returned numbers when using a Chinese locale, this causes problems in
applications that put the short month name and the day of the month together.

Spotted by: Ting-Wei Lan <lantw44 gmail com>