Markdown filter: some link related text does not get extracted

[Kuro Kurosaka]

In different ways of referencing URLs, some text that should be extracted are not extracted.

Case 1

Here, [this text should be extracted]

[this text should be extracted]: http://okapiframework.org/this/url/should/not/be/extracted

The visible reference text does not get extracted.

Case 2

[This anchor text should be extracted][Arbitrary case-insensitive reference text-should not be extracted]

[arbitrary case-insensitive reference text-should not be extracted]: http://okapiframework.org/do/not/extract/me

The anchor text doesn't get extracted.

Case 3

![translatable alt text][Invisible reference text should not be extracted]

[Invisible reference text should not be extracted]: http://okapiframework.org/wiki/images/f/f0/OkapiLargeLogo.png "title text should be extracted"

Neither the alt text or the title text gets extracted.

[Kuro Kurosaka]

Fixing issue 711. All Markdown filter unit tests pass.

→ <<cset f5d5c79a93a1>>

[Kuro Kurosaka]

The fix has been merged in pull request #234.