* dir.cc (mkdir): Call set_file_attribute with additional handle

	* dir.cc (mkdir): Call set_file_attribute with additional handle
	argument.
	* fhandler.cc (fhandler_base::fchmod): New method.
	* fhandler.h: Declare fchmod method in fhandler_base,
	fhandler_disk_file and fhandler_virtual.
	* fhandler_disk_file.cc (fhandler_disk_file::fchmod): New method.
	(fhandler_base::open_fs): Call set_file_attribute with additional
	handle argument.
	* fhandler_virtual.cc (fhandler_virtual::fchmod): New method.
	* path.cc (symlink_worker): Call set_file_attribute with additional
	handle argument.
	* security.cc (get_nt_object_security): New function.
	(get_nt_object_attribute): Call get_nt_object_security.
	(set_nt_attribute): Add handle argument.  Call get_nt_object_security
	first, read_sd only if that fails.
	(set_file_attribute): Add handle argument.
	* security.h (set_file_attribute): Declare with additional handle
	argument.
	* syscalls.cc (stat_suffixes): Move to beginning of file.
	(chown_worker): Call set_file_attribute with additional handle argument.
	(chmod): Reorganize to call fhandler's fchmod method eventually.
	(fchmod): Ditto.