Compatibility: EMS 3.2+
Expects: AX    4600H
Returns: AH    EMM status (0=successful)
AL    EMM version number in BCD (e.g., 32H is EMM 3.2; 40H = 4.0)
Info: Use this to ensure that the installed version supports any
special features you wish to access.

Notes: EMM 4.0 has been standard since 1987 and it is usually quite safe
to assume 4.0 is present.  Furthermore, in most cases, you can
get by without using any of the features unique to 4.0.

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INT 67H 4600H: Get EMM Version Number