cf-serverd: free getaddrinfo() result, on error of OpenReceiverChannel()

getaddrinfo() may allocate the 'result' struct even in cases where it
will return an error. Take care to free memory, although we would exit
the server process anyway.
cf-serverd: getaddrinfo() will use a numeric port, no lookup

This `AI_NUMERICSERV` flag avoids looking up the "services" table for
a string port resolution, according to the manual.
cf-serverd: getaddrinfo() will NOT set "errno" upon failure

It has its own `gai_strerror()` function to resolve its (reentrant)
result code.
cf-serverd: fix typo for addrinfo constant

As spotted by Dimitrios Apostolou
Correct vzps usage
Redmine#5271: pluck set_field_value
Redmine#5271: do not INFORM erroneously if setting an empty field to an empty value, just note it in VERBOSE
Print errno related string when SSL_read/write fail with SSL_ERROR_SYSCALL. Also moved a docstring to the proper place.
Changed wording to something nicer.
docstring fix.
SO_REUSEADDR missing is not a reason to WARN loudly. Demote to VERBOSE.
Demoted to VERBOSE the instructions on how to trust a new client.
Fix wording when trust fails, so that messages are not so aggressive.

Also Change wording in serverd messages from host to peer.
Amended @ediosyncratic's nitpicks.
Fix /0 CIDR matching, it was triggerring undefined behaviour.
Update verify_users_pam.c

Updated for bug https://cfengine.com/dev/issues/5485 as requested by Volker Hilsheimer. 
This will allow compile on NetBSD.
Tested on NetBSD i386 version 6.1.3.
Merge pull request #1663 from fkruchio/master

Update verify_users_pam.c
Merge pull request #1658 from jimis/minor

Reduce and beautify messages related to TLS protocol and trust on keys.
Merge pull request #1661 from jimis/cidr_fix

CIDR fix for /0 in IPv4.
Redmine #5380: Introduce privilege elevation in Windows testing.

This is needed in order to run tests as a user other than
Administrator, even if that user has admin privileges. The reason is
that Windows by default runs every process with non-admin rights, so
we need to elevate the privileges ourselves.