All changes:
- fix check of tags in lines: check lines without tags, fix check of tags with
negation ("!tag")
- add string functions string_split_tags and string_free_split_tags
- add tests on function gui_line_match_tags
The pointer and index returned is now the first element found with the value
(with the lower index if there are many elements with same value).
And the index for insert is the last element with same value + 1
(the higher index + 1).
Sébastien Helleu