Add tests for legacy Unicode data files

Add tests for legacy Unicode data files

There are 5 files in lib/unicore/To that may be in direct use by
applications, and which are not used by Perl itself.  These have been
changed in an earlier stable release to have comments in them saying,
their use is deprecated, and that Unicode::UCD gives a stable API for
access to the data they contain.  However, no warning is given if an
application reads these files, so the deprecation cycle needs to be
quite long.  Until we decide to get rid of these files sometime in the
future, we should make sure they exist and are correct.  Since they
aren't actually used by Perl, there were no such tests.  This commit
adds some tests.  It puts them in lib/Unicode/UCD.t, as that required
the least amount of work, as it already has nearly all the
infrastructure required for testing these.