Added header guards to files in directory vcl/

Change-Id: I76ad0c34f2b107d56e92c5a6a8f4c61554c93e2f
Reviewed-on: https://gerrit.libreoffice.org/9597Reviewed-by: Thomas Arnhold <thomas@arnhold.org>
Tested-by: Thomas Arnhold <thomas@arnhold.org>