Int 67 Fn 4321  - Q87 V4+ - Installation Check                             [u]

   AX = 4321h
   EAX = 87654321h (entire EAX value required)

Return: EAX = 12345678h if Q87 is installed

Note:  this call requires that VCPI services be available; if they are not,
     this call will not be recognized
BUG:   v4.00-v4.03 will hang on most machines when run under bare DOS with
     no memory manager, because neither Q87 nor UNLOAD87 checks whether
     there is a valid INT 67 handler before performing an installation
     check via INT 67

See Also: AX=2833h,INT 21/AX=4321h