cfengine_stdlib.cf now lives in "libraries"

Fixes #2724
Redmine#2753: add acceptance test
Some small test cleanups to make it more cross platform friendly.
Merge pull request #723 from kacfengine/tzzTest

Acceptance test for Redmine 2753.
POLICY_SERVER can't be NULL

If it is, it's a bug.
getaddrinfo should fail when given an empty nodename

...fix this in the getaddrinfo() we provide in libcompat. Previously empty
nodename was being treated like NULL nodename.
Ensure we are always reading/writing IP address for policy_server

...and not hostnames, mostly in file policy_server.dat but also whenever we
assign to the POLICY_SERVER global variable.

Provide IsIPAddress() for this purpose which uses system's getaddrinfo(),
tested in tests/unit/isipaddress_test.

Also converted some unsafe string assignments (silent truncations) to safe
failures in case of error.
Add comment explaining glibc's breakage.

Thanks mvpel@githug (Michael Pelletier) for the insight.