MFC 259910, 260023, 260028, 260600 & 260701:
o   Fix "kptdir is itself virtual" error, caused by having the kptdir in PBVM.
o   Allow building a cross libkvm for ia64.
o   Add support for virtual cores (aka minidumps).
o   We don't have to worry about page sizes when working on virtual cores.
o   Handle truncation of the size returned by _kvm_kvatop().