cmd/internal/gc: convert yet more Node fields to bools

Convert Embedded, Method, and Colas to bools.

I believe that this is the last of the Node fields
that can be trivially converted to bools.

No functional changes. Passes toolstash -cmp.

Change-Id: I81962ee47866596341fc60d24d6959c20cd7fc1c
Reviewed-on: https://go-review.googlesource.com/8440
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
diff --git a/src/cmd/8g/gsubr.go b/src/cmd/8g/gsubr.go
index 929cbae..76c67af 100644
--- a/src/cmd/8g/gsubr.go
+++ b/src/cmd/8g/gsubr.go
@@ -1732,7 +1732,7 @@
 	var oary [10]int64
 	var nn *gc.Node
 	o := gc.Dotoffset(n, oary[:], &nn)
-	if nn != nil && nn.Addable != 0 && o == 1 && oary[0] >= 0 {
+	if nn != nil && nn.Addable && o == 1 && oary[0] >= 0 {
 		*n1 = *nn
 		n1.Type = n.Type
 		n1.Xoffset += oary[0]