INT 2F - MS Windows - SWITCH VMs AND CALLBACK                                   
	AX = 1685h
	BX = VMsee Virtual Machine ID of virtual machine to switch to
	CX = flags (see #02717)
	DX:SI = priority boost (refer to VMM.INC)
	ES:DI -> FAR procedure to callback
Return: CF set on error
	    AX = error code
		01h invalid VMsee Virtual Machine ID
		02h invalid priority boost
		03h invalid flags
	CF clear if successful
	    event will be or has been called
Notes:	some DOS devices, such as networks, need to call functions in a
	  specific VMsee Virtual Machine. This call forces the appropriate VMsee Virtual Machine to be installed.
	the callback procedure must preserve all registers and return with IRET
SeeAlso: AX=1683h,INT 15/AX=1117h,AX=DB06h"WINGO"


Bitfields for VMsee Virtual Machine switching flags:
Bit(s)	Description	(Table 02717)
 0	wait until interrupts enabled
 1	wait until critical section unowned
 2-15	reserved (zero)