This regression seems more severe than the bug the commit was
attempting to fix (incorrect parsing of nested wikilinks in normal
links), so that bug is reintroduced until localization-aware parsing
that allows us to detect file links is added.

This commit partially reverts fac60dee48.

Signed-off-by: odidev <odidev@puresoftware.com>

* Proposed fix for https://github.com/earwig/mwparserfromhell/issues/197

* Port the fix for #197 to the C tokenizer

* Fix parsing of external links where the URL is terminated by some special character

- One existing test case has been found wrong -- current MediaWiki
  version always terminates the URL when an opening bracket is
  encountered.
- Other test cases added: double quote, two single quotes and angles
  always terminate the URL (regardless if it is a free link or external
  link inside brackets). One single quote does not terminate the URL.

* Fix case-insensitive parsing of URI schemes