gitweb: bugfix: git_print_page_path() needs the hash base

gitweb: bugfix: git_print_page_path() needs the hash base

If a file F exists in branch B, but doesn't exist
in master branch, then blob_plain needs the hash base in
order to properly get the file.  The hash base is passed
on symbolically so we still preserve the "latest" quality
of the link presented by git_print_page_path().

Signed-off-by: Luben Tuikov <ltuikov@yahoo.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>