Add overriding class for LTR

Can then use for things like passwords, which should be left-to-right regardless of language.

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5521 2fea6a4d-a838-0410-917b-93a53c48e9d2
Merge remote-tracking branch 'upstream/master'