INT 21 - DOS 5+ - SET EXECUTION STATE

	AX = 4B05h
	DS:DX -> execution state structure (see #01625)
Return: CF clear if successful
	    AX = 0000h
	CF set on error
	    AX = error code (see #01680 at AH=59h/BX=0000h)
Note:	used by programs which intercept AX=4B00h to prepare new programs for
	  execution (including setting the DOS version number).	 No DOS, BIOS
	  or other software interrupt may be called after return from this call
	  before commencement of the child process.  If DOS is running in the
	  HMA, A20 is turned off on return from this call.
SeeAlso: AH=4Bh