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, 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>