XPcpu()
  This function returns the CPU type as a number
------------------------------------------------------------------------------

   Function:   XPcpu()

               CPcpu() is a function that will test the CPU, and return a
               indicating what type of CPU is has found. Currently CPcpu()
               differentiates betweeem 8086, 286, 386 and 486 CPUs. An even
               tighter differentiation could have been possible, but this is
               about as precise as you would want to be in a Clipper
               Application.

               As promised in the previous version of the Library, XPcpu()
               now also tests for the presence of a 486.

               This Function can be more accurate that XPromid(), as it
               actually tests the CPU, XPromid() merely looks for an ID
               byte in the Computer's ROM.

   Syntax:     XPcpu() --> nCPU

   Arguments:  None

   Returns:    One of the following numbers: 86, 286, 386 or 486.
               Indicating what CPU it has found in the machine.

   Usage:      if XPcpu() < 386
                 ? 'I want to run on a bloody i386 or higher, okay?'
                 quit
               endif