It turns out that TIM1 and TIM8 have their own Capture/Compare
interrupt vector. For all of the other timers, the capture/compare
interrupt vector is the same as the update vector.
So we need to add handlers for these vectors and enable them
when using capture/compare callbacks.
During testing of this, I also found that passing a channel callback
into the channel constructor would not enable interrupts properly.
I tested using:
```
>>> pyb.Timer(1, freq=4).channel(1, pyb.Timer.OC_TOGGLE, callback=lambda t: print('.', end=''))
```
I tested the above with channels 1, 4, and 8
This type was used only for the typedef of mp_obj_t, which is now defined
by the object representation. So we can now remove this unused typedef,
to simplify the mpconfigport.h file.
The machine_ptr_t type is long obsolete as the type of mp_obj_t is now
defined by the object representation, ie by MICROPY_OBJ_REPR. So just use
void* explicitly for the typedef of mp_obj_t.
If a port wants to use something different then they should define a new
object representation.
Only tuple, namedtuple and attrtuple use the tuple_cmp_helper function,
and they all have getiter=mp_obj_tuple_getiter, so the check here is only
to ensure that the self object is consistent. Hence use mp_check_self.