INT 31 P - DPMIsee DOS Protected-Mode Interface 0.9+ - ALLOCATE REAL MODE CALLBACK ADDRESS
	AX = 0303h
	DS:(E)SI = selector:offset of procedure to call
	ES:(E)DI = selector:offset of real mode call structure (see #03148)
Return: CF clear if successful
	    CX:DX = segment:offset of real mode call address (see #03149)
	CF set on error
	    AX = error code (DPMIsee DOS Protected-Mode Interface 1.0+) (8015h) (see #03143)
Notes:	the real mode call structure is static, causing reentrancy problems;
	  its contents are only valid at the time of a callback
	the called procedure must modify the real mode CS:IP(Internet Protocol) The lower level (transport layer) of the TCP/IP protocol suite.	See also TCP, TCP/IP. before returning
	values are returned to real mode by modifying the real mode call struc
	DPMIsee DOS Protected-Mode Interface hosts must provide at least 16 callbacks per client
	the limited DPMIsee DOS Protected-Mode Interface host built into Phar Lap's 286|DOS-Extender v2.5 does
	  not support this function
BUG:	Windows NT 4.0 either ignores or clears the high 16 bits of EDI,
	  causing an illegal instruction error if the real mode call
	  structure's offset in ES is greater than 64K
SeeAlso: AX=0304h,AX=0C00h


(Table 03149)
Values DPMIsee DOS Protected-Mode Interface real-mode callback procedure is called with:
	DS:(E)SI = selector:offset of real mode SS:SP
	ES:(E)DI = selector:offset of real mode call structure
	SS:(E)SP = locked protected mode API(Application Program[ming] Interface) The defined set of calls which a program may make to interact with or request services of the operating system or environment under which it is running.  Because the inputs and outputs of the calls are well-defined, a program using the API can continue using the identical calls even if the internal organization of the program providing the API changes. stack
	interrupts disabled
Return: (with IRET)
	ES:(E)DI = selector:offset of real mode call structure to restore