Sort attributes by name for display, to make order arch-independent.

Sort attributes by name for display, to make order arch-independent.

When data file attributes or variable attributes were displayed by
e.g. DISPLAY ATTRIBUTES or SYSFILE INFO, they were sorted in hash
order, which varies by architecture.  Therefore, the tests that
depended on this order failed on big-endian machines such as mips.
This commit fixes the problem by displaying attributes in sorted
order.

This fixes a failure in the "Perl copying system files" reported
by Debian buildds.