gotwebd: drop redundant NULL check qs is guaranteed to be not NULL reached that point.

gotwebd: remove useless comment should be placed further down, after BLOB and RSS are handled, but the call to `gotweb_render_header' is successfully clear on its own.

gotwebd: add an RSS feed for the tags ok tracey@

gotwebd: templateify gotweb_render_commits ok tracey@

gotwebd: templateify gotweb_render_navs ok tracey@

gotwebd: drop index_page_str and page_str gotwebd uses sprintf to update index_page_str and page_str if they were negative. While this specific usage is safe, let's drop it. Since the index_page_str and page_str fields are never read from, remove them. This saves two allocations per request too. ok tracey@

gotwebd: fix broken navigation in commits page since 8d02314 ok tracey@

gotwebd: start using the template system ok tracey@

gotwebd: simplify bit of gotweb_process_request ok tracey

gotwebd: provide maximum value for the description and cloneurl ok stsp@

gotwebd: rework gotweb_get_repo_{description,cloneurl} - use openat(2) since we've already opened the containing dir - use fstat(2) instead of multiple seeks - don't special case len == 0 ok and improvements by stsp

gotwebd: drop unused path parameter from got_get_repo_{owner,age} ok jamsek

gotwebd: simplify gotweb_render_index - drops the double loop; paginate in one go - avoid lstat + got_path_dir_is_empty for each entry: use dt_type if provided by the underlying filesystem - fixes a memleak: before `continue' we need to call gotweb_free_repo_dir ok stsp

gotwebd: use prev_disp to decide when to we've reached max_repos instead of hardcoding d_i - 2 and so expecting only "." and ".." as skipped entries, use t->prev_disp that is the number of repositories traversed until now (both skipped due to the pagination and the ones actually rendered.) ok jamsek

gotwebd: fix memleak in error path ok stsp@