since the lines in the parser have all newline characters removed, \s+ will
not match empty comments.
Added an example that makes other tests fail without this patch.
the current implementation of items marked obsolete did not allow "plain"
comments for these items. However, this is perfectly fine according to
the original gettext tools. When writing a po file, comments for obsolete
items don't contain the '#~ ' mark (tested using msgcat), so this is now
also aligned with the behaviour of the original gettext tools.
For all these cases I added examples in the po files, that failed with the
current implementation and work fine after these changes.
Some languages (such as Polish, Russian or Romanian) do have more
complicated plural forms. Those are still expressible by a more
complicated mathematical expression. However, the msgmerge tool of
gettext will in these cases write multiline header fields. When parsing
such files with this lib, the headers get screwed up, so this patch
provides an example (from a pl_PL po file) and fixes this by joining the
lines in the header, before doing the actual parsing.
The gettext format specifies a msgctxt field for translated items. An
example of how to use this field has been added to the tests and the
parsing of this attribute has been implemented.
