Fix complaints about VT-x/AMD-V on CPUs lacking this feature

Detect CPU features and disable VT-x/AMD-V and related options on VM if needed.

Note: on machines lacking VT instructions, a strange complaint remains "VT-x is not available (VERR_VMX_NO_VMX)" if CPU number is not set to 1, so i forced it. (even on a machines with 4 cpus...)