Add support for HTTP/1.0 Persistent Connections to phttpget.  Requests are be marked as HTTP/1.1 but "Connection: Keep-Alive" is added; this convinces HTTP/1.0 servers and proxies to hold the TCP connection open despite not being able to use HTTP pipelining.
Add support for HTTP/1.0 Persistent Connections to phttpget.  Requests are
be marked as HTTP/1.1 but "Connection: Keep-Alive" is added; this convinces
HTTP/1.0 servers and proxies to hold the TCP connection open despite not
being able to use HTTP pipelining.

This dramatically cuts down on the number of TCP connections (and thus port
numbers) used by portsnap when talking to an HTTP/1.0 proxy (e.g., squid),
and has the side benefit of improving performance in those cases.

Tested by:	simon
Approved by:	re (kensmith)
MFC After:	1 week

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