md_links.pl -- Markdown reference link parser

Parses and removes reference links from the stream of symbol codes. Replaces line ends with canonical line ends.

 md_link(?Id, ?Url, ?Title) is det
Retrieves recorded link from the last invocation of md_links/2.
 md_links(+CodesIn, -CodesOut) is det
Same as md_links/3 but stores links in threadlocal predicate which is cleared on each invocation of this predicate.
 md_links(+CodesIn, -CodesOut, -Links) is det
Markdown reference link definition parser. Removes link definitions from the symbol code list.