Compatibility: EMS 4.0+
Expects: AX    5100H
BX    desired new size, in 16K pages
DX    EMM Handle (as obtained via INT 67H 4300H)
                                                                  
Returns: AH    EMM status (0=successful)
                                                                  
Info: Expands or shrinks the size of an EMS allocation.

When increasing the size of the allocation, the data in the
currently-allocated pages is retained.

Resizing to 0 (CX=0000H) does NOT free up a handle; be sure to
free the handle (via fn INT 67H 4500H) before terminating your
application.

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INT 67H 5100H: Resize EMS Handle