* io/Makefile (routines): Add sendfile and sendfile64.

* io/Makefile (routines): Add sendfile and sendfile64.

	(headers): Add sys/sendfile.h to the list.
	* sysdeps/unix/sysv/linux/Makefile (sysdep_headers): Don't add it here.
	* sysdeps/unix/sysv/linux/sys/sendfile.h: Moved to ...
	* io/sys/sendfile.h: ... here.
	* sysdeps/generic/sendfile.c: New file.
	* sysdeps/generic/sendfile64.c: New file.
	* sysdeps/unix/sysv/linux/Versions (GLIBC_2.1, GLIBC_2.3):
	Move sendfile, sendfile64 to ...
	* io/Versions (GLIBC_2.1, GLIBC_2.3): ... here.
	* sysdeps/mach/hurd/sendfile.c: New file.
	* sysdeps/mach/hurd/sendfile64.c: New file.

	* sysdeps/mach/nanosleep.c: New file.