TC: void fnmerge( char *path, const char *drive,
		   const char *dir, const char *name, const char *ext)


	- prototype in dir.h

	- makes a file name (path) from drive, dir, name, and ext
	- dir can include subdirectories
	- maximum sizes for these strings are:

	  MAXPATH  80	path
	  MAXDRIVE  3	drive - includes colon (:)
	  MAXDIR   66	dir - includes leading/trailing backslashes
	  MAXFILE   9	name
	  MAXEXT    5	ext, including leading dot (.)

	- invertible with fnsplit()