tools: libxl: remove libxl_domain_build_state from the IDL

tools: libxl: remove libxl_domain_build_state from the IDL

This datastructure is internal to the library.

Remove the reference from libxl_device_console. This could never have
been used from outside libxl and is only used internally to add the
primary PV console to a guest. Make an internal variant of
libxl_device_console_add which takes the build state as a parameter
instead.

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>