Use tag dispatch to better handle both NetworkInterface and NetworkStack
pointers.
The previous design was intended to avoid ambiguities when presented
with a scenario like
class MyDevice : public NetworkInterface, public NetworkStack {
};
TCPSocket(&MyDevice);
// Need NetworkStack *: use NetworkInterface::get_stack or
// cast to NetworkStack?
But the previous solution didn't actually work as intended. The overload
pair
nsapi_create_stack(NetworkStack *);
// versus
template <class IF>
nsapi_create_stack(IF *);
would only select the first form if passed an exact match -
`NetworkStack *`. If passed a derived class pointer, like `MyDevice *`,
it would select the template.
This meant that an ambiguity for MyDevice was at least avoided, but
in the wrong direction, potentially increasing code size.
But in other cases, the system just didn't work at all - you couldn't
pass a `MyStack *` pointer, unless you cast it to `NetworkStack *`.
Quite a few bits of test code do this.
Add a small bit of tag dispatch to prioritise the cast whenever the
supplied pointer is convertible to `NetworkStack *`.
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.
Added more tests, improved the existing ones. setblocking tests were not checking anything, so they were removed and these functions are called in TCPSocket tests instead.
Add functional and line coverage for UDPSocket and TCPSocket. The EventFlagsstub and NetworkStackstub classes are allowed to store multiple return values to allow running internal loops multiple times.