INT 21 - DOS 2+ - "RENAME" - RENAME FILE
	AH = 56h
	DS:DX -> ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. filename of existing file (no wildcards, but see below)
	ES:DI -> ASCIZA NUL-terminated ASCII string.	The ASCIZ string "ABC" consists of the four bytes 41h, 42h, 43h, and 00h.  Unless otherwise specified, maximum lengths given in the interrupt list do not include the terminating NUL. new filename (no wildcards)
	CL = attribute mask (server call only, see below)
Return: CF clear if successful
	CF set on error
	    AX = error code (02h,03h,05h,11h) (see #01680)
Notes:	allows move between directories on same logical volume
	this function does not set the archive attribute
	  (see #01420 at AX=4301h), which results in incremental backups not
	  backing up the file under its new name
	open files should not be renamed
	(DOS 2.x only) this function renames file by creating a new directory
	  entry with the new name, then marking the old entry deleted
	(DOS 3.0+) allows renaming of directories
	(DOS 3.1+) wildcards are allowed if invoked via AX=5D00h, in which case
	  error 12h (no more files) is returned on success, and both source and
	  destination specs must be canonical (as returned by AH=60h).
	  Wildcards in the destination are replaced by the corresponding char
	  of each source file being renamed.  Under DOS 3.x, the call will fail
	  if the destination wildcard is *.* or equivalent; under DR DOS 5.0,
	  the call will fail with error code 03h if any wildcards are used.
	  When invoked via AX=5D00h, only those files matching the attribute
	  mask in CL are renamed.
	under the FlashTek X-32 DOS extender, the old-name pointer is in DS:EDX
	  and the new-name pointer is in ES:EDI (DS must equal ES)
BUG:	(DR DOS 3.41) when invoked via AX=5D00h, this function will generate
	  a new directory entry with the new name (including any wildcards)
	  which can only be removed with a sector editor
SeeAlso: AH=17h,AX=4301h,AX=43FFh/BP=5053h,AX=5D00h,AH=60h,AX=7156h
SeeAlso: AX=F257h/SF=04h