Event equality.

- Implemented polymorphic equality, unit tests for all events other
 than unrecog.

Unrecog is changing. Equality comes after.
Type alias updates.

- Replaced all instances of uint8_t with val_t.
- Removed local typedefs for circular buffer.
events::unrecognized_c now only contains a single val_t.
s/recognized?/recog/g
Renamed s/recognize?/recog/g.