tests: add a more complete test for blocks in lists

https://bugzilla.gnome.org/show_bug.cgi?id=723417
New MarkDown parser

Much more robust and complete MarkDown parser inspired by
ParseDown http://parsedown.org/

https://bugzilla.gnome.org/show_bug.cgi?id=723417
Add support for mixed markup and markdown

https://bugzilla.gnome.org/show_bug.cgi?id=723417
Add support for literal and link span type markdown

https://bugzilla.gnome.org/show_bug.cgi?id=723417
Don't attempt to markup inside <> tags

https://bugzilla.gnome.org/show_bug.cgi?id=723417
Use the markdown parser as the primary way of expanding gtkdoc markup

https://bugzilla.gnome.org/show_bug.cgi?id=723417
Add test case for mixed docbook sections

https://bugzilla.gnome.org/show_bug.cgi?id=723417
Add support for header ids in markdown

https://bugzilla.gnome.org/show_bug.cgi?id=723417