internal/syscall/windows/registry: handle invalid integer values

I have around twenty of such values on a Windows 7 development machine.
regedit displays (translated): "invalid 32-bits DWORD value".

Change-Id: Ib37a414ee4c85e891b0a25fed2ddad9e105f5f4e
Reviewed-on: https://go-review.googlesource.com/9901
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

src/internal/syscall/windows/registry/value.go

@@ -175,8 +175,14 @@ func (k Key) GetIntegerValue(name string) (val uint64, valtype uint32, err error
 	}
 	switch typ {
 	case DWORD:
+		if len(data) != 4 {
+			return 0, typ, errors.New("DWORD value is not 4 bytes long")
+		}
 		return uint64(*(*uint32)(unsafe.Pointer(&data[0]))), DWORD, nil
 	case QWORD:
+		if len(data) != 8 {
+			return 0, typ, errors.New("QWORD value is not 8 bytes long")
+		}
 		return uint64(*(*uint64)(unsafe.Pointer(&data[0]))), QWORD, nil
 	default:
 		return 0, typ, ErrUnexpectedType