gitweb: Show '...' links in "summary" view only if there are more items

gitweb: Show '...' links in "summary" view only if there are more items

Show "..." links in "summary" view to shortlog, heads (if there are
any), and tags (if there are any) only if there are more items to show
than shown already.

This means that "..." link is shown below shortened shortlog if there
are more than 16 commits, "..." link below shortened heads list if
there are more than 16 heads refs (16 branches), "..." link below
shortened tags list if there are more than 16 tags.

Modified patch from Jakub to to apply cleanly to master, also preform
the same "..." link logic to the forks list.

Signed-off-by: Jakub Narebski <redacted>
Signed-off-by: Robert Fitzsimons <redacted>
Signed-off-by: Junio C Hamano <redacted>