Markdown renders incorrect link, when URL contains colon (BB-10228)

Found by accident, when using Wikimedia's GeoHack tool.

A "normal" URL (doesn't contain colon):

http://toolserver.org/~geohack/geohack.php?project=osm&params=50_15_N_19_00_E

renders correctly – example.

When URL contains colon (:):

http://toolserver.org/~geohack/geohack.php?project=osm&params=50_15_N_19_00_E_type:city

It renders a link to current page – example

(edit source of this issue, to see, that the same URL as above is given in this link).