vdagent-x11: Add set_error_handler / restore_error_handler helpers
vdagent-x11: Add set_error_handler / restore_error_handler helpers

This is #if 0-ified for now, to avoid breaking compilation with -Werror.

Signed-off-by: Hans de Goede <9fa1be1a5b5729e4c6b404f34c9ce49ff4882fd8@redhat.com>

elmarco/vdagent-gtk,elmarco/vdagent-gtk,elmarco/vdagent-gtk