xl: add some example configuration files

xl: add some example configuration files

These are much more minimal than the equivalent xmexamples but should
eventually reference a more complete document describing the available options.

These are based on the guest configuration files that I actually use day-to-day.

There is an unresolved reference to a document describing the complete syntax.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Ian Jackson <ian.jackson.citrix.com>
Committed-by: Ian Jackson <ian.jackson.citrix.com>