To turn ssa compilation on or off altogether, use
-ssa=1 or -ssa=0.  Default is on.

To turn on or off consistency checks, do
-d=ssa/check/on or -d=ssa/check/off.  Default is on for now.

Change-Id: I277e0311f538981c8b9c62e7b7382a0c8755ce4c
Reviewed-on: https://go-review.googlesource.com/20217Reviewed-by: David Chase <drchase@google.com>