RBIL61 - INT 31 - DPMI 0.9+ - FREE REAL MODE CALLBACK ADDRESS {protected mode}

INT 31 P - DPMIsee DOS Protected-Mode Interface 0.9+ - FREE REAL MODE CALLBACK ADDRESS
	AX = 0304h
	CX:DX = real mode callback address
Return: CF clear if successful
	CF set on error
	    AX = error code (DPMIsee DOS Protected-Mode Interface 1.0+) (8024h) (see #03143)
Note:	the limited DPMIsee DOS Protected-Mode Interface host built into Phar Lap's 286|DOS-Extender v2.5 does
	  not support this function
SeeAlso: AX=0303h