INT 2F CU - NETWORK REDIRECTOR (DOS 4.0+) - EXTENDED OPEN/CREATE FILE
	AX = 112Eh
	SS = DS = DOS DS
	ES:DI -> uninitialized SFTsee System File Table for file
	STACK: WORD file attribute for created/truncated file
			low byte = file attributes
			high byte = 00h normal create/open, 01h create new file
	SDAsee Swappable Data Area first filename pointer -> fully-qualified filename
	SDAsee Swappable Data Area extended file open action = action code
	      (see #01770 at INT 21/AX=6C00h)
	SDAsee Swappable Data Area extended file open mode = open mode for file (see INT 21/AX=6C00h)
Return: CF set on error
	    AX = error code
	CF clear if successful
	    CX = result code
		01h file opened
		02h file created
		03h file replaced (truncated)
	    SFTsee System File Table initialized (except handle count, which DOS manages itself)
Note:	this function is called by the DOS 4.0+ kernel
BUG:	this function is not called correctly under some DOS versions
	  (at least 5.0 and 6.2):
	    the file attribute on the stack is not correct if the action
	      code is 11h,
	    the result code in CX is not passed back to the application.
SeeAlso: AX=1115h,AX=1116h,AX=1117h,INT 21/AX=6C00h