INT 21 P - Phar Lap 386/DOS-Extender v3.0+ - READ/WRITE SYSTEM REGISTERS        
	AX = 2535h
	EBX = direction (00h read registers, 01h write)
	DS:EDX -> system register record (see #01375)
Return: CF clear
Note:	this call is only available under MS Windows if PHARLAP.386 VDD is
	  installed


Format of Phar Lap system register record:
Offset	Size	Description	(Table 01375)
 00h	DWORDDoubleword; four bytes.	 Commonly used to hold a 32-bit segment:offset or selector:offset address.	CR0
 04h  4 DWORDs	DR0,DR1,DR2,DR3
 14h  2 DWORDs	reserved
 1Ch  2 DWORDs	DR6,DR7
 24h  3 DWORDs	reserved