Printable mode cleanup. Now done through stylesheets, <link>ed so that the
print command on a regular page will actually use the print stylesheet.
Explicitly following the printable link will also show the printable view
CAVEATS: IE/Win may oversimplify the link style in what should be colored
or underlined text. Page title is not shown in Nostalgia skin printable
view. Part of the footer is duplicated in the output and will be visible in a styleless
user agent (lynx, really old Netscape, etc). Some render options aren't
totally handled right for printable, such as ? brokenlinks.
Also, section edit links are now available in diff view if the dest rev is
the current revision.
Some misc code clean-up and formatting as well.