Wikitextparser

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- Improve handling of extension tags inside external links. (49)
- Ignore invalid attributes that do not start with space characters. (48)

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- Improved how invalid attributes (in html tags, tables, etc.) are handled. (47)

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- Fixed a bug in handling ``<pre>`` tags. (46)

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- Fixed a bug in parsing tag attributes. (44)

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- Fixed handling of tags having different casings in start and end name, e.g. ``<s></S>``.
- Fix handling of extension tags.
- Fixed a bug in ``get_bolds``/``get_italics`` resulting in duplicate items in returned values. It also was causing a subtle issue in ``plain_text``/``remove_markup``, too. (42)
- Fixed detection of parameters containing single braces.

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- Fix handling of external links containing wikilinks.