)
Call DELWATCH private entry point with:
	AH = function
	    00h (OS hook) installation check
		AL = 00h required for DELWATCH 1.x
		Return: CF clear
			AX = 0000h
			CX = 0004h (unsupported function)
	    01h (DELWATCH 1.x) New Disk
	        ???
	    01h (DELWATCH 2.0+) disable DELWATCH on drive
		AL = drive number (00h = A:)
		Return: AX = status (0000h if failed, FFFFh if successful)
	    02h (OS hook) Delete File
		AL = drive number (00h = A:)
		DX = directory cluster number (0000h for root directory)
		CX = directory entry number
		DS:BX -> directory entry
		ES,DS must be valid selectors if called in protected mode
		Return: DS:BX -> updated directory entry
			CF set if file is to be deleted by the OS
			CF clear if DELWATCH has placed the file in its queue
		Note:	deletes the directory entry
	    03h	(OS hook) Free Clusters
		AL = drive number (00h = A:)
		CX = number of clusters currently free (do not free if > 1)
		DX = preferred 'search from cluster' (ignored by DELWATCH 2.0)
		Return: CF clear if clusters freed
			CF set if no clusters freed
			DX = new 'search from' cluster (one before first free)
	    04h (OS hook) free root directory entry
		AL = drive number (00h = A:)
		Return: CF set if no directory entry freed
	    05h (OS hook) return free space
		AL = drive number (00h = A:)
		CX = number of free clusters
		Return:	CX = updated number of free clusters
		Notes:	adds space used by "deleted" files to free space
			call is chained
	    06h enable DELWATCH on drive
		AL = drive number with bit 7 set (80h = A:, etc.)
			(DELWATCH 2.0+: set bit 6 for removable drives)
		BX = maximum files of same name in one directory to save
		CX = maximum files to save on this disk
		DS:DX -> MEMDESC??? for drive data (see #04104)
		DS:SI -> MEMDESC??? for DWLIST (see #04104)
		ES,DS must contain valid selectors if called in protected mode
		Return: AX = status
			    0000h failed
			    FFFFh successful
			CX = error code on failure (see #04102)
			    (0004h "wrong version" if AL < 80h on entry)
	    07h (DELWATCH 1.x) disable DELWATCH on drive
		???
	    07h (DELWATCH 2.0+) (OS hook) new disk
		AL = drive (00h = A:, etc.)
		ES:BX -> DOS DDSC structure
		CF set if not enabled
		Return: ???
	    08h set file extensions list
		AL = sense (00h exclude named extensions, 01h only named ext.)
		DS:BX -> 31-byte ASCIZ extension list (three blank-padded bytes
			  per extension)
		Return: AX = FFFFh (successful)
	    09h	adjust pending delete space
		AL = drive number (00h = A:)
		CX = number of clusters being freed
		Return: AX = 0000h if drive not enabled
	    0Ah remove DELWATCH entry
		AL = drive number (00h = A:)
		DX = directory cluster number (0000h if root directory)
		CX = directory entry number
		BX:SI -> filename
		ES,DS must contain valid selectors if called in protected mode
		Return: AX > 0000h if entry found in DWLIST
	    0Bh enable NEWDISK
		Return: AX > 0000h if successful (FFFFh for DELWATCH 2.0)
		see also function 0Dh
	    0Ch (DELWATCH 1.x) drive status
		AL = drive number (00h = A:, etc.)
		Return: AX = drive data segment, 0000h if not enabled
			CX = pending delete space, if drive enabled
	    0Ch (DELWATCH 2.0+) check if drive enabled
		AL = drive number with bit 7 set (80h = A:, etc.)
		DS:DX -> MEMDESC for drive data (see #04104)
			(DX = 0000h if not required)
		DS:SI -> MEMDESC for DWLIST (see #04104)
			(SI = 0000h if not required)
		ES,DS must contain valid selectors if called in protected mode
		Return: AX = drive status (see also #04103)
			    0000h disabled or error
				CX = error code (see #04102)
			    0001h drive enabled
				CX = pending delete space, FFFFh if NEWDISK
				      not yet called
	    0Dh disable NEWDISK
		BX = segment address of bitmap buffer
		Return: AX > 0000h if successful (FFFFh for DELWATCH 2.0)
		see also function 0Bh
	    0Eh (DELWATCH 2.0+) (OS hook) purge file
		AL = drive number (00h = A:)
		DX = directory cluster number (0000h if root directory)
		CX = directory entry number
		Return: CF set if drive not enabled
			CF clear
			    AX = status
				0000h successfully purged
				else error code (see #04102)
	    0Fh (DELWATCH 2.0+) (OS hook) undelete file
		AL = drive number (00h = A:)
		DX = directory cluster number (0000h if root directory)
		CX = directory entry number
		Return: CF set if drive not enabled
			CF clear
			    AX = status
				0000h successfully undeleted
				else error code (see #04102)
Return: AX = 0000h, CX = 0001h (see #04102) if DELWATCH busy
	registers unchanged if AH > 0Fh on entry
Notes:	functions marked "OS hook" must under no circumstances by called by
	  external applications, as this would bypass the serialization
	  performed by the kernel and cause problems at least in multitasking
	  environments.
	two functions have been swapped between DELWATCH 1.x and DELWATCH 2.0
	  to ensure that DELWATCH 1.x calls will not do anything under newer
	  versions of the OS; for the same reason, the drive number in AL
	  sometimes requires that bit 7 be set for DELWATCH 2.0+.
SeeAlso: AX=1001h,AX=1010h