xm: Remove redundant validity checks, clean up function headers
xm: Remove redundant validity checks, clean up function headers

Arguments for driver entry points are checked in libvirt.c, so no need to
check again. Make function entry points consistent. Don't type caste the
privateData.

andreabolognani/libvirt,zippy2/libvirt,trainstack/libvirt,crobinso/libvirt,shugaoye/libvirt,elmarco/libvirt,siboulet/libvirt-openvz,zhlcindy/libvirt-1.1.4-maintain,siboulet/libvirt-openvz,datto/libvirt,jfehlig/libvirt,elmarco/libvirt,shugaoye/libvirt,cbosdo/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,iam-TJ/libvirt,iam-TJ/libvirt,iam-TJ/libvirt,fabianfreyer/libvirt,zhlcindy/libvirt-1.1.4-maintain,fabianfreyer/libvirt,datto/libvirt,jfehlig/libvirt,olafhering/libvirt,crobinso/libvirt,eskultety/libvirt,agx/libvirt,eskultety/libvirt,nertpinx/libvirt,eskultety/libvirt,jardasgit/libvirt,zippy2/libvirt,rlaager/libvirt,jardasgit/libvirt,taget/libvirt,zippy2/libvirt,taget/libvirt,elmarco/libvirt,datto/libvirt,olafhering/libvirt,cbosdo/libvirt,andreabolognani/libvirt,libvirt/libvirt,jardasgit/libvirt,trainstack/libvirt,jardasgit/libvirt,trainstack/libvirt,iam-TJ/libvirt,trainstack/libvirt,nertpinx/libvirt,eskultety/libvirt,zhlcindy/libvirt-1.1.4-maintain,fabianfreyer/libvirt,siboulet/libvirt-openvz,agx/libvirt,zhlcindy/libvirt-1.1.4-maintain,zippy2/libvirt,cbosdo/libvirt,rlaager/libvirt,datto/libvirt,nertpinx/libvirt,rlaager/libvirt,trainstack/libvirt,jfehlig/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,cbosdo/libvirt,olafhering/libvirt,trainstack/libvirt,VenkatDatta/libvirt,iam-TJ/libvirt,libvirt/libvirt,elmarco/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,zhlcindy/libvirt-1.1.4-maintain,taget/libvirt,andreabolognani/libvirt,datto/libvirt,agx/libvirt,iam-TJ/libvirt,libvirt/libvirt,cbosdo/libvirt,crobinso/libvirt,trainstack/libvirt,shugaoye/libvirt,rlaager/libvirt,agx/libvirt,iam-TJ/libvirt,elmarco/libvirt,andreabolognani/libvirt,eskultety/libvirt,shugaoye/libvirt,nertpinx/libvirt,libvirt/libvirt,rlaager/libvirt,shugaoye/libvirt,crobinso/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,taget/libvirt,siboulet/libvirt-openvz,olafhering/libvirt,siboulet/libvirt-openvz,agx/libvirt,taget/libvirt,nertpinx/libvirt