TC: char *parsfnm( const char *cmdline, struct fcb *fcbptr, int option)

	- prototype in dos.h

	- parses command line cmdline for a file name, placing it into a
	  FCB as drive/filename/file ext, pointed to by fcbptr
	- option is same as AL in MS-DOS function call INT 21,29
	- returns pointer to byte beyond end of filename, 0=error