Before this, all code sources were like "#: code:foo/bar.py:0", now
they will have line no like "#: code:foo/bar.py:123".
Note that the gettext() wouldn't be affected, since it doesn't consult
the file name or line so far.
bzr revid: p_christ@hol.gr-20101229113306-vo3gflwunq2f75qm