Override 'wdgi.url_scheme' via a request header, 'X_WSGI_URL_SCHEME'.

Allows proxies which serve mixed HTTP / HTTPS requests to control signal
which are served as HTTPS.
Speling
Enforce that 'X_WSGI_URL_SCHEME' must be one of 'http' or 'https'.
Switch to using the quasi-standard 'X_FOWRARDED_PROTO' header.
Typo.
Fix: start_response() should only re-raise exc_info if headers have been written
Merge from master.
Normalize long kwargs (one per line).
Add 'trusted_proxy' adjustment.
Only allow trustted proxies to overried request.urlscheme.
Document the 'trusted_proxy' bit.
Merge pull request #42 from Pylons/feature.x_wsgi_url_scheme-header

Override 'wsgi.url_scheme' via a request header, 'X_WSGI_URL_SCHEME'.
Fix typo in waitress-serve example
Merge pull request #57 from olt/patch-1

Fix typo in waitress-serve example
typo in docs
Merge pull request #59 from jor123/patch-1

tiny typo in docs
sharing code with bert
Replace magic numbers with errno.X

This fixes the code so that running under OS X it raises
ConnectionClosed as appropriate for when the connection is reset by
peer.
multiprocessing.Queue() is holding onto resources ...

And it means we run out of file descriptors to use on OS X when running
tests...
Upon a socket.error, we need to close the filehandle

If we don't close the filehandle, socket.close() won't actually close
the underlying file descriptor because the fp still holds a reference to
it. Even when it then goes out of scope, the file pointer is still open.