* src/xen_unified.c et al: Unified Xen driver.  Architecture
	  described here:
	  https://www.redhat.com/archives/libvir-list/2007-March/msg00396.html

  warnings when compiling without Xen
Daniel

  src/Makefile.am src/libvirt.c src/qemu_internal.c src/test.c
  src/xen_internal.c src/xen_internal.h src/xend_internal.c
  src/xm_internal.c src/xml.c src/xs_internal.c
  tests/Makefile.am tests/sexpr2xmltest.c tests/xmconfigtest.c:
  allow selective compilation of Xen,QEmu/KVM and test support
  in or out at configure time. Also allows to compile on a system
  without Xen development installed. All drivers are selected by
  default.
Daniel