cmd/compile: remove two unnecessary Pkg fields

Exported is no longer used since removing the text-format exporter,
and Safe is only used within importfile so it can be made into a local
variable.

Change-Id: I92986f704d7952759c79d9243620a22c24602333
Reviewed-on: https://go-review.googlesource.com/29115
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/cmd/compile/internal/gc/go.go

@@ -22,9 +22,7 @@ type Pkg struct {
 	Pathsym  *obj.LSym
 	Prefix   string // escaped path for use in symbol table
 	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
 }
 

src/cmd/compile/internal/gc/main.go

@@ -810,6 +810,7 @@ func importfile(f *Val, indent []byte) {
 	}
 
 	// process header lines
+	safe := false
 	for {
 		p, err = imp.ReadString('\n')
 		if err != nil {
@@ -819,10 +820,13 @@ func importfile(f *Val, indent []byte) {
 			break // header ends with blank line
 		}
 		if strings.HasPrefix(p, "safe") {
-			importpkg.Safe = true
+			safe = true
 			break // ok to ignore rest
 		}
 	}
+	if safemode && !safe {
+		Yyerror("cannot import unsafe package %q", importpkg.Path)
+	}
 
 	// assume files move (get installed)
 	// so don't record the full path.
@@ -867,10 +871,6 @@ func importfile(f *Val, indent []byte) {
 		Yyerror("no import in %q", path_)
 		errorexit()
 	}
-
-	if safemode && !importpkg.Safe {
-		Yyerror("cannot import unsafe package %q", importpkg.Path)
-	}
 }
 
 func pkgnotused(lineno int32, path string, name string) {