[libre-riscv-dev] daily kan-ban update 21may2020

[Michael Nolan]

This morning I fixed the broken test_adde (it broke because I hadn't 
added overflow support to caller.py). I think today I'll work on 
changing the CR unit to take in the individual cr bitfields instead of 
the whole CR as well as adding the necessary bits to the decoder to 
handle that. If I finish that, I'll work on more formal verification.

--Michael