is also start with "\n", but msgctxt is inserted before it, to avoid msgfmt(1)'s
format mismatch check (`msgid' and `msgstr' entries do not both begin with '\n')
old NetBSD versions and to strip msgctx if requested by the package.
This allows to replace the use of msgfmtstrip in various packages by
setting MSGFMT_STRIP_MSGCTX.