int int86( int intr_num, union REGS *inregs, union REGS *outregs )

	- prototype in dos.h

	- executes 8086 software interrupt specified by intr_num
	- copies register values from inregs into the registers
	- if CF is set, an error has occurred
	- preserves SP register so calls to INT 25 and INT 26 via this
	  function don't require a stack adjustment
	- unique to DOS
	- see	int86x()  intdos()   intdosx()   intr()   REGS