Add ELB proxy protocol support to the HTTP module.

Previously, this was only supported with http-socket.  If you're
using http-socket, you probably have a webserver on top of you--and if
you have that, then uWSGI isn't receiving the proxy protocol anyway.
Merge pull request #627 from blue-goji/proxy-protocol-for-http-module

Add ELB proxy protocol support to the HTTP module.
allow to enable the proxy protocol management only in the http router
Implement a new metric option 'reset_after_push' which will make uWSGI...

reset to 0 the given metric after it's been pushed to the stats backend.
This is handy when you want to automatically reset counters every 'freq'
seconds.
Update all plugins so that they bear this functionality (reset_after_push)
Add new functions 'uwsgi_metric_set_min' & 'uwsgi_metric_set_max', which...

push respectively a absolute value if she is less than or greater than
that the previous push.

Refactore the function uwsgi_metric_set_min
Exposure of 'uwsgi_metric_set_min' & 'uwsgi_metric_set_max' for python interface.
Use the wlock when the value is reseted
Merge pull request #630 from btall/reset-after-push

Implement a new metric option 'reset_after_push' which will make uWSGI.....
various metrics fixes for reset_after_push feature
when changing metrics we need a write lock
Doesn't use uwsgi_metric_get for the comparison on uwsgi_metric_set_max and uwsgi_metric_set_min (it introduce a deadlock)
try to honour chmod/chown socket in fd0 mode
hack for avoiding Safari iOS to make mess with keepalive
postpone uwsgi_as_root() call
less invasive privileges drop when chown-socket is in place
Merge pull request #631 from btall/set-min-set-max

Add new functions 'uwsgi_metric_set_min' & 'uwsgi_metric_set_max', wh…
fixed log setup when both --logto and --log2, fixes unbit/uwsgi#635
Merge pull request #636 from prymitive/issue635

fixed log setup when both --logto and --log2, fixes unbit/uwsgi#635
retry on mule_get_msg EAGAIN