Expects: AX    0001H
ES:BX address of first byte to test
CX    size, in bytes, of memory region to test
Returns: CF    Carry Flag is clear (NC) is successful and...
AX    result code: 0000H = global memory
0001H = global and local memory
0002H = local memory
Info: Use a FAR call to the switcher entry address (see INT 2fH 4b02H)
to learn whether a particular block of memory is global or local
to the current session.  Local memory areas are replaced whenever
a session switch occurs.

One use for this is to find out if your application or TSR
program code is stored in global memory (started before the task
switcher), or local memory (started in a task-switcher session).
Global TSRs are never swapped out.

INT 2fH 4bxxH (switcher functions)
- -

SwSrvc Fn 0001H: Test Memory Region