Regression tests for link backtracking optimizations:
.
[[some unrelated text [link]

[link]: foo
.
<p>[[some unrelated text <a href="foo">link</a></p>
.


This is not a valid emphasis, because \n considered a whitespace:
.
**test
**

**
test**

**
test
**
.
<p>**test
**</p>
<p>**
test**</p>
<p>**
test
**</p>
.


Link label has priority over emphasis (not covered by commonmark tests):
.
[**link]()**

**[link**]()
.
<p><a href="">**link</a>**</p>
<p>**<a href="">link**</a></p>
.


Issue #55:
.
![test]

![test](foo bar)
.
<p>![test]</p>
<p>![test](foo bar)</p>
.


Issue #35. `<` shoud work as punctuation
.
an **(:**<br>
.
<p>an <strong>(:</strong><br></p>
.


Should unescape only needed things in link destinations/titles:
.
[test](<\f\o\o\>\\>)
.
<p><a href="%5Cf%5Co%5Co%3E%5C">test</a></p>
.

.
[test](foo "\\\"\b\a\r")
.
<p><a href="foo" title="\&quot;\b\a\r">test</a></p>
.


Not a closing tag
.
</ 123>
.
<p>&lt;/ 123&gt;</p>
.


Not a list item
.
1.list
.
<p>1.list</p>
.


Normalize link destination, but not text inside it:
.
<http://example.com/α%CE%B2γ%CE%B4>
.
<p><a href="http://example.com/%CE%B1%CE%B2%CE%B3%CE%B4">http://example.com/αβγδ</a></p>
.


Autolinks do not allow escaping:
.
<http://example.com/\[\>
.
<p><a href="http://example.com/%5C%5B%5C">http://example.com/\[\</a></p>
.


Multiline title in definitions:
.
[foo]: test '
1
2
3
'

[foo]
.
<p><a href="test" title="
1
2
3
">foo</a></p>
.


Coverage. Directive can terminate paragraph.
.
a
<?php
.
<p>a</p>
<?php
.


Coverage. Nested email autolink (silent mode)
.
*<foo@bar.com>*
.
<p><em><a href="mailto:foo@bar.com">foo@bar.com</a></em></p>
.


Coverage. Unpaired nested backtick (silent mode)
.
*`foo*
.
<p><em>`foo</em></p>
.


Coverage. Entities.
.
*&*

*&#x20;*

*&amp;*
.
<p><em>&amp;</em></p>
<p><em> </em></p>
<p><em>&amp;</em></p>
.


Coverage. Escape.
.
*\a*
.
<p><em>\a</em></p>
.


Coverage. parseLinkDestination
.
[foo](<
bar>)

[foo](<bar)
.
<p>[foo](&lt;
bar&gt;)</p>
<p>[foo](&lt;bar)</p>
.


Coverage. parseLinkTitle
.
[foo](bar "ba)

[foo](bar "ba\
z")
.
<p>[foo](bar &quot;ba)</p>
<p><a href="bar" title="ba\
z">foo</a></p>
.


Coverage. Image
.
![test]( x )
.
<p><img src="x" alt="test"></p>
.
.
![test][foo]

[bar]: 123
.
<p>![test][foo]</p>
.
.
![test][[[

[bar]: 123
.
<p>![test][[[</p>
.
.
![test](
.
<p>![test](</p>
.
.
![test]( x =100x200)
.
<p><img src="x" alt="test" width="100" height="200"></p>
.
.
![test]( x =x)
.
<p><img src="x" alt="test"></p>
.
.
![test]( x =100x)
.
<p><img src="x" alt="test" width="100"></p>
.
.
![test]( x =x200)
.
<p><img src="x" alt="test" height="200"></p>
.
.
![test]( x "title" =100x200)
.
<p><img src="x" alt="test" title="title" width="100" height="200"></p>
.
.
![test]( x =WxH )
.
<p>![test]( x =WxH )</p>
.
.
![test]( x = 100x200 )
.
<p>![test]( x = 100x200 )</p>
.
.
![test]( x =aaaxbbb )
.
<p>![test]( x =aaaxbbb )</p>
.
.
![test](http://this.is.test.jpg =100x200)
.
<p><img src="http://this.is.test.jpg" alt="test" width="100" height="200"></p>
.
.
![test](<x =100x200)
.
<p>![test](&lt;x =100x200)</p>
.
.
![test](<x> =100x200)
.
<p><img src="x" alt="test" width="100" height="200"></p>
.
.
![test](test =100%x)
.
<p><img src="test" alt="test" width="100%"></p>
.

Coverage. Link
.
[test](
.
<p>[test](</p>
.

Coverage. Reference
.
[
test\
]: 123
foo
bar
.
<p>foo
bar</p>
.