Support IPv6-only hosts in httpslib, simpler IPv6 SSL.Connection

httpslib was not able to connect to IPv6-only hosts because
SSL.Connection uses IPv4 by default, and httpslib was not doing anything
to override this.

The attached patch modifies HTTPSConnection.connect() to use
getaddrinfo() and to iterate over provided addresses, similarly to
HTTPConnection.connect().

To do this, SSL.Connection() gets an additional optional parameter
specifying the address family of the underlying socket.

To test:
> h = M2Crypto.httpslib.HTTPSConnection(host = 'hostname', port=55555);
> h.request('GET', '/foo'); print h.getresponse().read()
against a TLS server, with "hostname" pointing to a v6-only address.

https://bugzilla.osafoundation.org/show_bug.cgi?id=13044
https connections over a proxy are broken in Python >=2.6

* Python 2.6 introduced its own support for https over proxies using
  CONNECT; this has changed the behavior of
  urllib2.Request.get_selector() to again only return the host-relative
  /path instead of the full URL, but
  M2Crypto.httpslib.ProxyHTTPSConnection expects the full URL.

* Recent (2.6 or 2.7) httplib.HTTPConnection.endheaders() got
  a parameter; M2Crypto.httpslib.ProxyHTTPSConnection calls it without
  the parameter.

The attached patch fixes both problems, tested on Python 2.[567].

Longer-term, m2crypto should probably transition to the Python's native
support for CONNECT proxies, but that would require changing the minimum
version requirement to 2.6, or perhaps providing an alternative
implementation for older versions.  This is intended to be a minimal and
compatible fix.

https://bugzilla.osafoundation.org/show_bug.cgi?id=13049
test_ssl tests for ssl23 are broken on recent OpenSSL

OpenSSL has added support for TLS 1.1 and 1.2, which means the
-no_{ssl3,tls1} options to still allow the new TLS versions.

The test suite expects the server to use specific versions of
protocols; modify it to explicitly enable only the protocols that
we need (which should always work) instead of trying to disable
all alternatives (which will break over time as new protocols are
added).

https://bugzilla.osafoundation.org/show_bug.cgi?id=13072