Work around smart HTTP bugs in C Git

Work around smart HTTP bugs in C Git

I have unfortunately introduced a few bugs in the native Git client
over the years. 1.7.5 is unable to send chunked requests correctly,
resulting in corrupt data at the server. Ban this client whenever
it uses chunked encoding with an error message.

Prior to some more recent versions, git push over HTTP failed to
report status information and error messages due to a race within
the client and its helper process. Check for these bad versions and
send errors as messages before the status report, enabling users
to see the failures on their terminal.

Change-Id: Ic62d6591cbd851d21dbb3e9b023d655eaecb0624