Align seekdir and telldir API to POSIX definition.

	Align seekdir and telldir API to POSIX definition.
	* Makefile.in (NEW_FUNCTIONS): Remove seekdir and telldir mappings.
	* dir.cc (telldir): Move functionality from telldir64 here.  Use
	long, rather than _off_t.
	(telldir64): Just call telldir.  Only keep for backward compatibility.
	(seekdir): Move functionality from seekdir64 here.  Use long, rather
	than _off_t.
	(seekdir64): Just call seekdir.  Only keep for backward compatibility.
	* fhandler.h: Throughout, change prototypes of seekdir and telldir
	methods to use long, rather than _off64_t.
	* fhandler_disk_file.cc: Change aforementioned methods accordingly.
	* fhandler_netdrive.cc: Ditto.
	* fhandler_registry.cc: Ditto.
	* fhandler_virtual.cc: Ditto.
	* include/sys/dirent.h (struct __DIR): Change __d_position from
	_off_t to long to reflect API change.
	(telldir): Change prototype to use long, rather than off_t.
	(seekdir): Ditto.