go/importer: revert incorrect change that slipped in prior CL

The package of anonymous fields is the package in which they were
declared, not the package of the anonymous field's type. Was correct
before and incorrectly changed with https://golang.org/cl/18549.

Change-Id: I9fd5bfbe9d0498c8733b6ca7b134a85defe16113
Reviewed-on: https://go-review.googlesource.com/18596Reviewed-by: Alan Donovan <adonovan@google.com>

src/go/internal/gcimporter/gcimporter.go

@@ -492,12 +492,10 @@ func (p *parser) parseField(parent *types.Package) (*types.Var, string) {
 		// anonymous field - typ must be T or *T and T must be a type name
 		switch typ := deref(typ).(type) {
 		case *types.Basic: // basic types are named types
-			pkg = nil
+			pkg = nil // objects defined in Universe scope have no package
 			name = typ.Name()
 		case *types.Named:
-			obj := typ.Obj()
-			pkg = obj.Pkg()
-			name = obj.Name()
+			name = typ.Obj().Name()
 		default:
 			p.errorf("anonymous field expected")
 		}