INT 2F - SRSoft MODAL PCIBM PC v2+ - GET ALL COMMON VARIABLES AND SEMAPHORES
	AX = AB04h
	DS:DX -> buffer for common data
Return: AX = 5253h ('SR' byte-swapped) if installed
	CF clear if successful
	CF set on error
SeeAlso: AX=AB00h"MODAL",AX=AB03h"MODAL",AX=AB05h"MODAL",AX=AB06h,AX=AB07h