cmd/compile/internal/gc: convert fields of Pkg to bool

Convert Pkg.Imported, Pkg.Exported, Pkg.Direct from uint8/int8/int8 to bool.

This change passes go build -toolexec 'toolstash -cmp' -a std.

Change-Id: I67a71f1186ff9737c03eca413f7d35d8a79ebc9b
Reviewed-on: https://go-review.googlesource.com/14371
Run-TryBot: Dave Cheney <dave@cheney.net>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/cmd/compile/internal/gc/go.go b/src/cmd/compile/internal/gc/go.go
index 3e7d6aa..21e6486 100644
--- a/src/cmd/compile/internal/gc/go.go
+++ b/src/cmd/compile/internal/gc/go.go
@@ -125,9 +125,9 @@
 	Path     string // string literal used in import statement
 	Pathsym  *Sym
 	Prefix   string // escaped path for use in symbol table
-	Imported uint8  // export data of this package was parsed
-	Exported int8   // import line written in export data
-	Direct   int8   // imported directly
+	Imported bool   // export data of this package was parsed
+	Exported bool   // import line written in export data
+	Direct   bool   // imported directly
 	Safe     bool   // whether the package is marked as safe
 	Syms     map[string]*Sym
 }