Currently this uses the same mechanism used by the rtos to conditionally
include the network-socket API. Perhaps this should be builtin to the
config system?
Note: this does require that the bug-compatible inclusion of mbed.h
be removed to avoid include-order issues.
per @sg-
- Adopt C++11 style template arguments, requires rename to Callback
- Add constructor for C style callback functions
- Add constructor for Callbacks
- Add static function for passing to C style callbacks