* autoload.cc (NtSetSecurityObject): Add.

	* autoload.cc (NtSetSecurityObject): Add.
	* fhandler_disk_file.cc (fhandler_disk_file::fchmod): Only request
	READ_CONTROL rights when opening the file.
	* ntdll.h (NtSetSecurityObject): Add declaration.
	* security.cc (write_sd): Call NtSetSecurityObject instead of
	BackupWrite.
	(get_nt_object_security): Don't free security descriptor here.

	* syscalls.cc (ttyname): Use buffer of length TTY_NAME_MAX + 1.
	* sysconf.cc (sysconf): Handle _SC_TTY_NAME_MAX request.
	* include/limits.h: Define TTY_NAME_MAX and _POSIX_TTY_NAME_MAX.