*	This function replaces the library version of getcwd().
 *
 * Results:
 *	The input and output are filesystem paths in native form. The result
 *	is either the given clientData, if the working directory hasn't
 *	changed, or a new clientData (owned by our caller), giving the new
 *	native path, or NULL if the current directory could not be determined.
 *	If NULL is returned, the caller can examine the standard posix error
 *	If NULL is returned, the caller can examine the standard Posix error
 *	codes to determine the cause of the problem.
 *
 * Side effects:
 *	None.
 *
 *----------------------------------------------------------------------
 */