This is the FreeBSD implementation, plus some tests. The FreeBSD
implementation includes the GNU extensions and seems to be what
iOS is using too, which should provide bug compatibility for app
developers.
The code unfortunately uses a lot of stack, and uses FreeBSD locale
implementation that we don't have, but it does seem better maintained
than the other BSDs.
Bug: http://b/29251134
Test: ran tests
Change-Id: Ie477b45e42a6df1319b25712098519d2b33adf67
f1c568d1ea