kvm-unit-tests : The first version of VMX nested test case

This is the first version for VMX nested environment test case. It
contains the basic VMX instructions test cases, including VMXON/
VMXOFF/VMXPTRLD/VMXPTRST/VMCLEAR/VMLAUNCH/VMRESUME/VMCALL. This patch
also tests the basic execution routine in VMX nested environment and
let the VM print "Hello World" to inform its successfully run.

New files added:
x86/vmx.h : contains all VMX related macro declerations
x86/vmx.c : main file for VMX nested test case

Signed-off-by: Arthur Chunqi Li <yzt356@gmail.com>