Add linksto: syntax to detect outoing links

Unfortunately the links are case sensitive.  Its sad, but that is required
to properly support things like wictionary.  We might be able to hack
something better to support case insisitive link search but I'm not sure its
worth it at this stage.

Bug: 69295
Change-Id: I5a1599d8fe67ad8a327f6c07397b301549423d82
Merge "Add linksto: syntax to detect outoing links"