i18n: translate each paragraph separately

Makes translation work easier by reducing message sizes and avoiding
invalidating whole messages on small changes or additions to the
original text.

Makefile

@@ -100,6 +100,7 b' i18n/hg.pot: $(PYTHON_FILES) mercurial/h'
 	  --copyright-holder "Matt Mackall <[e-mail]> and others" \
 	  --from-code ISO-8859-1 --join --sort-by-file \
 	  -d hg -p i18n -o hg.pot
+	$(PYTHON) i18n/posplit i18n/hg.pot
 
 %.po: i18n/hg.pot
 	msgmerge --no-location --update $@ $^

mercurial/i18n.py

@@ -36,7 +36,7 b' def gettext(message):'
     if message is None:
         return message
 
-    u = t.ugettext(message)
+    u = u'\n\n'.join([t.ugettext(m) for m in message.split('\n\n')])
     try:
         # encoding.tolocal cannot be used since it will first try to
         # decode the Unicode string. Calling u.decode(enc) really