QPID-4947: C++ Broker ACL restricts hosts from which users may connect.
This commit adds:
* Acl rule file "create connection host=hostname" support for allowing and denying connections.
* AclHost class to represent a host specified in the rule file.
* Global and user-specific lists of AclHost rules. Created by AclReader and consumed by AclConnectionCounter.
* Address range checks and other giblets in SocketAddress:
** asString support to hide IPv6 decoration and service (port) details.
** binary comparison of network addresses.
** new firstAddress function to complement existing nextAddress. Socket addrinfo for AclHost objects is computed once only for lifetime of Acl file load.
** Posix and Windows implementations are identical.
* New unit test for address comparisons. Testing a live broker is great but forcing connections to be from some arbitrary IPv4 or IPv6 address is hard. So there's a unit test for that.

Further discussion about this feature is in https://reviews.apache.org/r/23322

git-svn-id: https://svn.apache.org/repos/asf/qpid/trunk@1610874 13f79535-47bb-0310-9956-ffa450edef68