cmd/internal/gc: make Node.Isddd boolean

Convert Node.Isddd to a boolean and simplify usage.

- Node.Isddd converted to bool
- Type.Isddd converted to bool
- mkinlcall converted to take isddd as a bool
- typecheckaste converted to take isddd as a bool
- ascompatte converted to take isddd as a bool

Change-Id: I52586145619c44182bb0c2c5d80a0a3fe3e50a07
Reviewed-on: https://go-review.googlesource.com/7172
Reviewed-by: Keith Randall <khr@golang.org>
diff --git a/src/cmd/internal/gc/dcl.go b/src/cmd/internal/gc/dcl.go
index a9454e6..cccdbdd 100644
--- a/src/cmd/internal/gc/dcl.go
+++ b/src/cmd/internal/gc/dcl.go
@@ -1150,9 +1150,9 @@
 			n.Right.Op = OTARRAY
 			n.Right.Right = n.Right.Left
 			n.Right.Left = nil
-			n.Isddd = 1
+			n.Isddd = true
 			if n.Left != nil {
-				n.Left.Isddd = 1
+				n.Left.Isddd = true
 			}
 		}