simplify http / https handling

[seife]

instead of duplicating code for both WiFiClient and WiFiClientSecure,
use one pointer that gets assigned the corresponding class.

[schreibfaul1]

Thanks for the PR, maybe even destroy the _client object when not in use to save memory

[seife]

Thanks for the PR, maybe even destroy the _client object when not in use to save memory

No! At least not in the current implementation. Now it is just a pointer to the statically allocated client and clientsecure instances.

We could dynamically create it with new() and destroy it with delete(), but this needs exact tracking of the objects lifetime. See the check I added in streamavail() and the default (dummy) assignment of _client in setDefaults(): this is exactly to avoid crashes due to _client not yet being initialized, but already used by the application.

It's also worth questioning how much this saves actually, as many devices will have an instance of the LWIP stack active anyway. I personally would wote for less complexity :-)