Version bump: nginx 1.7.2

- Removed upsteam_check since the patch fails to apply
- Changed upstream url for ngx_metrics
Reintroduce the http_upstream_check module

Based on the 1.5.12+ patch. Filed upstream at:
https://github.com/yaoweibin/nginx_upstream_check_module/issues/33
Use $(get_libdir) instead of static for nginx 1.7.2

Fixes https://bugs.gentoo.org/show_bug.cgi?id=510040
Need to inherit multilib for get_libdir.
Merge branch 'nginx-1.7.2'