Use --no-location instead of --add-location=never

This fixes things for old versions of msgmerge such as the one
used on Travis CI (Ubuntu 14.04)

Signed-off-by: Daniel Axtens <dja@axtens.net>
Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>

po/Makevars

@@ -57,7 +57,7 @@ USE_MSGCTXT = no
 # Useful options are in particular:
 #   --previous            to keep previous msgids of translated messages,
 #   --quiet               to reduce the verbosity.
-MSGMERGE_OPTIONS = --add-location=never
+MSGMERGE_OPTIONS = --no-location
 
 # These options get passed to msginit.
 # If you want to disable line wrapping when writing PO files, add