- Make API more idiomatic (x holdUnless y, instead of holdUnless(x, y))
- Add new SeqMem API, readAndHold, which corresponds to most common
use of holdUnless
A lot of utility code was just being imported willy-nilly from one
package to another. This moves the common code into util to make things
more sensible. The code moved were
* The AsyncQueue and AsyncDecoupledCrossing from junctions.
* All of the code in rocket's util.scala
* The BlackBox asynchronous reset registers from uncore.tilelink2
* The implicit definitions from uncore.util
