RST does not allow nested emphasis, links, or other inline
constructs.
Closes#4581, double parsing of links with URLs as
link text. This supersedes the earlier fix for #4581
in 6419819b46.
Fixes#4561, a bug parsing with URLs inside emphasis.
Closes#4792.
Previously pandoc would sometimes combine two line blocks separated by blanks, and ignore trailing blank lines within the line block.
Test is checked to be consisted with http://rst.ninjs.org/
