INT 21 - DOS 1+ - SEQUENTIAL WRITE TO FCBsee File Control Block FILE
	AH = 15h
	DS:DX -> opened FCBsee File Control Block (see #01345)
	Disk Tranfer Area contains record to be written
Return: AL = status
	    00h successful
	    01h disk full
	    02h segment wrap in DTAsee Disk Transfer Address
Notes:	writes a record of the size specified in the FCBsee File Control Block beginning at the
	  current file position, then updates the current block and current
	  record fields in the FCBsee File Control Block
	if less than a full sector is written, the data is placed in a DOS
	  buffer to be written out at a later time
	not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=0Fh,AH=14h,AH=1Ah,AH=40h,INT 2F/AX=1109h