ANDQConst show up occassionally because of right shifting lowering.
ORs and XORs are already folded properly during generic.

Change-Id: I2f9134679555029c641264ce5333d70e167c65f7
Reviewed-on: https://go-review.googlesource.com/21375Reviewed-by: Keith Randall <khr@golang.org>
Run-TryBot: Alexandru Moșoi <alexandru@mosoi.ro>
TryBot-Result: Gobot Gobot <gobot@golang.org>