url: use new http support if requested by the user
The new http library is wired in via an extra module
(httpconnection.py), as it requires similar but different plumbing to
connect the library to Mercurial's internals and urllib2. Eventualy we
should be able to remove all of keepalive.py and its associated tangle
in url.py and replace it all with the code in httpconnection.py.
To use the new library, set 'ui.usehttp2' to true. The underlying http
library uses the logging module liberally, so if things break you can
use 'ui.http2debuglevel' to set the log level to INFO or DEBUG to get
that logging information (for example, ui.http2debuglevel=info.)
Import new http library as mercurial.httpclient.
This is revision
a4229f13c374 of
http://py-nonblocking-http.googlecode.com/ with a no-check-code
comment added to the end of each file using `for fi in $(hg manifest |
grep mercurial/httpclient/) ; echo '# no-check-code' >> $fi`.