libxl: change IDL to export a saner interface for upcoming language bindings

libxl: change IDL to export a saner interface for upcoming language bindings

Firstly remove an anonymous union in libxl_device_pci structure which
was making auto-generating language bindings more complicated than
necessary and exporting random bits of low level ABI that libxl that
would rather hide anyway. There is a corresponding (untested) change to
the ocaml binding which maintains previous ml API.

Secondly make the libxl_file_reference type a Builtin. This is a
'semantic
correctness' issue in that libxl ABI/API won't change. But it makes it
so that when the IDL is used to generate language bindings that a
file_reference type is not exported.

Also implement a Numeric type which all integers are derived from. Make
sure a boolean signed/unsigned attribute is set accordingly. This is
required to allow language bindings to correctly handle the sign bit in
environments with arbitrarily long integers.

Signed-off-by: Gianni Tedesco <gianni.tedesco@citrix.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>