Update #10994

CASE and BCASE were used by 5c in switch statements, cmd/compile
does not use them.

Change-Id: I7a578c461b52b94690e35460926849b28971b770
Reviewed-on: https://go-review.googlesource.com/14009Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Minux Ma <minux@golang.org>
Run-TryBot: Minux Ma <minux@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>