INT 16 - PC Tools v6.0+ PCRUN API - ???
AX = FFDDh
BX = 000Bh
???
Return: CX = 5555h if PCRUN active
DX = 5555h
Note:   also clears flag set by AX=FFDDh/BX=000Ah


16FFDDBX000B - PC Tools v6.0+ PCRUN API - ???