Use xgettext --no-location in make update-pot

This avoid the large diff we have that is mostly caused by the
line numbers changing in the po/pot files.

po/makefile

@@ -40,6 +40,8 @@ $(POTFILES) : $(PO)/%.pot :
 	cat $(PO)/domains/$*/*.srclist > $(PO)/POTFILES_$*.in
 	$(XGETTEXT) --default-domain=$* --directory=$(BASE) \
 	  --add-comments --foreign --keyword=_ --keyword=N_ \
+          # avoid the huge churn on each make update-pot
+          --no-location \
 	  --keyword=P_:1,2 \
 	  --files-from=$(PO)/POTFILES_$*.in -o $(PO)/domains/$*/c.pot.tmp
 	cmp --silent $(PO)/domains/$*/c.pot.tmp $(PO)/domains/$*/c.pot || \