Language files. The files are in standard ".po" format. They are
compiled using scripts/msgcompile.pl, which will interpret the
Content-Type/charset header (the X-PCC-Charset is no longer used).
Supported encodings for po files are utf-8 and iso-8859-1, the
compiler translates to UTF-8. To use arbitrary Unicode characters,
write "\\u1234" (not "\u1234", because that isn't understood by some
tools).
