On platforms where hardware timers are available, test these in each
combination of hard/soft and one-shot/periodic in the same way as for
software timers. Where a platform supports both software (id = -1) and
hardware (id >= 0) timers, the behaviour of both is now checked.
For now, esp8266 is the only platform that supports hardware timers and
both hard and soft callbacks.
Signed-off-by: Chris Webb <chris@arachsys.com>
