New test for LC_NUMERIC

[Petter Reinholdtsen]

I started with the fmon test, and rewrote it to use snprintf() and
LC_NUMERIC instead.  Will this be accepted as part of glibc?  How
should I submit it.  I can send it as a diff against tst-fmon.*, or
perhaps make the new files available on the web somewhere?

I called it tst-numeric, but perhaps tst-snprintf() is better?  I just
sets LC_NUMERIC, and calls snprintf() and compare the result.  I use
it with "%'g" to check the norwegian locales.