Stylesheets and patches for Debian gitweb

Simple adaption of the gitweb css to fit into the Debian redesign. The slightly modified gitweb.css stylesheet links to my standard debian.css stylesheet and inherits the formatting of the main elements.

The gitweb.cgi/index.cgi script need to be modified to include the debheader.html and debfooter.html files in the $site_header and $site_footer variable respectively