links 6.x-1.0

Fixed incorrect HTML rendering in links_weblink per issue #363597.

Added update #6103 which drops and recreates the indices
on the {links} table, an attempt to address #362967.

New feature: Administrative option allows rel="nofollow"
attribute on external links, per issue #144620.

New feature: Administrative option allows direct links
(skipping redirect page, at the cost of no click
counting). Separately controllable for internal and
external links.

New feature: Optional logging of all external redirects,
primarily for diagnostic purposes but also useful if the
site owner wants really detailed click tracking.

Added #maxlength attribute for URL textfields to allow
longer values, per issue #232575.