(Bug 26410) In an internal link, a plus sign is treated as a space if the link

(Bug 26410) In an internal link, a plus sign is treated as a space if the link
has a % sign in it, but interperted as a + if no % sign is present.

This changes how the parser interperts links slightly. However:
*I can't imagine anyone is relying on this behaviour
*Things should be consistent. a + sign shouldn't magically change meaning
if there is a % sign somewhere else in the link.
*Pages are allowed to contain % signs in their title, and + signs,
you should be able to link to such pages just by typing there name without
resorting to %2B.
*If you have a page named foo%+ having [[{{PAGENAME}}]] link to a different
page seems inherently wrong.
*The previous behaviour seemed accidental.