KVM, x86: add architectural support code for #VE

Dump the contents of the #VE info data structure and assert that #VE does
not happen, but do not yet do anything with it.

No functional change intended, separated for clarity only.

Extracted from a patch by Isaku Yamahata <isaku.yamahata@intel.com>.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>