cmd/compile: indicate sense of hash/bisect match in output
If a hash match is "disabled" (!enabled) indicate that in the
output with DISABLED. This is helpful in ensuring that multiple
package-directed command-line flags have the intended behavior,
e.g.
```
go build -a \
-gcflags=all=-d=gossahash=vn \
-gcflags=runtime=-d=gossahash=vy \
std
```
Output looks like
[DISABLED] [bisect-match 0x11d0ee166d9d61b4]
or (w/ "v"-prefixed hashcode )
sort/slice.go:23:29 note [DISABLED] [bisect-match 0xa5252e1c1b85f2ec]
gossahash triggered sort/slice.go:23:29 note [DISABLED]
100001011111001011101100
Change-Id: I797e02b3132f9781d97bacd0dcd2e80af0035cd8
Reviewed-on: https://go-review.googlesource.com/c/go/+/497216
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: David Chase <drchase@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>