chg: add pgid to hgclient struct The previous patch makes the server tell the client its pgid. This patch stores it in hgclient_t and adds a function to get it.

commandserver: send pgid in hello message See the next patches for why we need it.

tests: update test certificate generation instructions Suggestions from Anton Shestakov and Julien Cristau to use -subj and faketime, respectively.

sslutil: move comment about protocol constants protocolsettings() is the appropriate place for this comment.

sslutil: support defining cipher list Python 2.7 supports specifying a custom cipher list to TLS sockets. Advanced users may wish to specify a custom cipher list to increase security. Or in some cases they may wish to prefer weaker ciphers in order to increase performance (e.g. when doing stream clones of very large repositories). This patch introduces a [hostsecurity] config option for defining the cipher list. The help documentation states that it is for advanced users only. Honestly, I'm a bit on the fence about providing this because it is a footgun and can be used to decrease security. However, there are legitimate use cases for it, so I think support should be provided.

hghave: add test for Python 2.7+ Setting ciphers in the ssl module requires Python 2.7. Surprisingly, we didn't have a test for running on Python 2.7.