The HTTPResponse class now handles 100 continue responses, instead of
choking on them.  It detects them internally in the _begin() method
and ignores them.  Based on a patch by Bob Kline.

This closes SF bugs 498149 and 551273.

The FakeSocket class (for SSL) is now usable with HTTP/1.1
connections.  The old version of the code could not work with
persistent connections, because the makefile() implementation read
until EOF before returning.  If the connection is persistent, the
server sends a response and leaves the connection open.  A client that
reads until EOF will block until the server gives up on the connection
-- more than a minute in my test case.

The problem was fixed by implementing a reasonable makefile().  It
reads data only when it is needed by the layers above it.  It's
implementation uses an internal buffer with a default size of 8192.

Also, rename begin() method of HTTPResponse to _begin() because it
should only be called by the HTTPConnection.