New members are added to the network interface
-getaddrinfo
-getaddrinfo_async
gethostbyname is unchanged but gethostbyname_async result param now contains results od DNS records found.
Test cases for sync/async added added to DNS test folder.
New classes covered with unit tests: SocketAddress, EthernetInterface, EMACInterface, WiFiAccessPoint.
Also added missing namespace in front of mbed::Callback usages.
EMACInterface is covered by the EthernetInterface unit tests.
Improved the stubs for event queue and nsapi_dns, to allow checking if callback are handled correctly. This involves some memory allocation and deallocation.
The NetworkStackWrapper is not covered as it seems to be deprecated code.