INT 21 P - Phar Lap 386/DOS-Extender - ISSUE REAL-MODE INTERRUPT                
	AX = 2511h
	DS:EDX -> parameter block (see #01361)
Return: all segment registers unchanged
	EDX unchanged
	all other registers contain values set by the real-mode int handler
	the flags are set as they were left by the real-mode interrupt handler
	real-mode register values are returned in the parameter block
Note:	this function is also supported by FlashTek X-32VM
SeeAlso: AX=2503h,AX=2505h,AX=250Eh,AH=E3h"OS/286",INT 31/AX=0300h


Format of Phar Lap real-mode interrupt parameter block:
Offset	Size	Description	(Table 01361)
 00h	WORD	interrupt number
 02h	WORD	real-mode DS value
 04h	WORD	real-mode ES value
 06h	WORD	real-mode FS value
 08h	WORD	real-mode GS value
 0Ah	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	real-mode EAX value
 0Eh	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	real-mode EDX value
Note: all other real-mode values set from protected-mode registers