* Add fast_timer_t that is 16-bit or 32-bit based on architecture
A 16-bit timer will overflow sooner but be faster to compare on AVR.
* Avoid 8-bit timer overflows in debounce algorithms
Count down remaining elapsed time instead of trying to do 8-bit timer
comparisons.
Add a "none" implementation that is automatically used if DEBOUNCE is
0 otherwise it will break the _pk/_pr count down.
* Avoid unnecessary polling of the entire matrix in sym_eager_pk
The matrix only needs to be updated when a debounce timer expires.
* Avoid unnecessary polling of the entire matrix in sym_eager_pr
The matrix only needs to be updated when a debounce timer expires.
The use of the "needed_update" variable is trying to do what
"matrix_need_update" was added to fix but didn't work because it only
applied when all keys finished debouncing.
* Fix sym_defer_g timing inconsistency compared to other debounce algorithms
DEBOUNCE=5 should process the key after 5ms, not 6ms
* Add debounce tests
Joel Challis
Simon Arlott