Merge branch 'jn/web' (early part)

* 'jn/web' (early part):
  gitweb: Add "next" link to commit view
  gitweb: Add title attribute to ref marker with full ref name
  gitweb: Do not show difftree for merges in "commit" view
  gitweb: SHA-1 in commit log message links to "object" view
  gitweb: Hyperlink target of symbolic link in "tree" view (if possible)
  gitweb: Add generic git_object subroutine to display object of any type
  gitweb: Show target of symbolic link in "tree" view
  gitweb: Don't use Content-Encoding: header in git_snapshot