tools: libxc: remove functions made obsolete by libxendevicemodel

tools: libxc: remove functions made obsolete by libxendevicemodel

This removes those functions which are obsolete _and_ are backed by a
stable hypercall interface.

xc_{set,get}_hvm_param were already deprecated in favour of
xc_hvm_param_{set,get} and were only retained due to QEMU's use.

Various functions relating to management of emulated IRQs are no
longer needed here now.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
---
Must be applied after qemu-trad has been updated to include:
   Switch from xc_{set,get}_hvm_param to xc_hvm_param_{set,get}
   Port to use libxendevicemodel
but this needn't happen in lockstep (i.e. in this exact commit)