Fix warnings related to po
Originally reported by: hahnjo
Fix warnings related to po
Individual commits:
- Build lilypond-doc in Documentation/po
This avoids warning messages from langdefs.py which tries to load
that locale domain and is also imported during a 'normal' build
while producing the .texi and .info files in Documentation/.
- Inline po-* targets into po/
Documentation/po/ has a custom po-update.
http://codereview.appspot.com/551830043
Original URL: https://sourceforge.net/p/testlilyissues/issues/5932