gitweb: Navbar refactoring - use git_page_nav to generate navigation bar
Use git_page_nav subroutine to generate navigation bar. Additional
navigation (either formats or pager/pagination) is put into variables.
Corrects error in git_search where hash parameter was added to
"summary" link instead of to "log" link. Might differ from previous
version by additional "<br/>" in navigation bar.
Signed-off-by: Jakub Narebski <jnareb@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>