tools: Bump some library sonames

tools: Bump some library sonames

libxc (libxenctrl, libxenguest):
   New claim_enabled field in struct xc_dom_image;
   New nr_outstanding_pages field in struct xc_dominfo;
   New fields in struct xc_hvm_build_args (xenguest.h).

libxl:
   new fields in dominfo domain_build_info device_vfb device_vkb
     device_disk etc. etc. etc.
   libxlu #includes libxl headers so needs to inherit its new soname
   Use Xen version for new sonames since we don't in fact guarantee
   ABI (as opposed to API) stability across releases.

xenstore (libxenstore):
   New flag XS_UNWATCH_FILTER, so bump minor version only.

This was the result of reviewing the output from:
  git-checkout staging
  cd tools
  git-diff RELEASE-4.2.2 `find -name \*.h`

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