Links in Trac should have :visited styles

[westonruter]

It is not helpful that links with both unvisited and visited states have the same color:

/* =Link Colors */
a:link,
a:visited,
dt em,
.milestone .info h2 em,
#content.build h2.config :link,
#content.build h2.config :visited,
.report div.reports h3 em {
	color: #21759b;
}

​http://wordpress.org/style/trac/wp-trac.css?12

I suggest we add a separate color for :visited, just as has been done for :hover:

a:visited {
    color: black;
}

[kpdesign]

I agree that we need a visited state for Trac links, but it should match the a:visited color being used elsewhere on wordpress.org. From style/wp4.css?38:

a:visited {
  color: #4ca6cf;
}

[nacin]

In 179:

Trac CSS: Remove a:visited styling, which overrides the global WP.org style (which is properly a different color).

props westonruter, kpdesign.
fixes #46.