INT 21,11 - Search for First Entry Using FCB

	AH = 11h
	DS:DX = pointer to unopened FCB

	on return:
	AL = 00 if matching file found
	   = FF if file not found

	- searches for first occurrence of filename specified in FCB
	- FCB must have drive id, filename, and extension before call
	- extended FCB can be used to specify a search criteria based
	  on attributes; hidden, system, label, and directory attributes
	  can be used to narrow the search  (see FILE ATTRIBUTES)
	- after successful call DTA holds an unopened FCB/XFCB for
	  the requested file.	Using any of the other FCB functions
	  destroys this DTA copy of the FCB/XFCB
	- searching can be continued with the FCB find-next function
	- "?" wildcard supported after DOS 2.1, "*" supported in DOS 3.x
	- DOS 2.x can't find . and .. entries, DOS 3.x can (unless in root)
	- see	INT 21,12