Remove bogus dependency on Ubuntu "localechooser-data" package

In Debian, this package doesn't exist as a .deb, so we must maintain our
own local copy of the languagelist file.

(This patch also adds code to synchronise this file to the Makefile's
"update:" target so this isn't too annoying.)

Signed-off-by: Chris Lamb <chris@chris-lamb.co.uk>