Remove the Addresser type. It isn't really necessary (the Address type
can change between OSes) and makes it difficult to fix a heap allocation
in interrupts (on the Nordic SoftDevices).
This is a backwards incompatible change, but only programs that use
SetConnectHandler should notice this.
This SoftDevice is used by default on the BBC micro:bit v2 so it's a
good idea to add support here.
Unfortunately this SoftDevice does not support scanning and connecting
to other devices. This means that I unfortunately had to duplicate the
event handler. I managed to refactor most other code to avoid
duplicating much more. (This is when macros would have been useful in
Go...)