Change to DBI $dbh->tables() API

DBI 1.201 (and soon 1.21) have a new quote_identifier method.
The tables method should use this to quote the identifiers it returns.
The DBI now provides a default quote_identifier method that does
standard SQL quote_identifier quoting (using double quotes).
Great.

But there's a problem for databases that require non-standard
quoting (DBD::mysql being the most widely used).

If I add calling quote_identifier into the default tables method
(that most drivers use) then any existing driver will get the
DBI's default quote_identifier method. For DBD::mysql, and some
others, tables() will now return names that are incorrectly quoted
and applications that try to use them will fail.

Here's how I'm currently thinking of handling the issue:

    =item C<tables> I<NEW>
     
    B<Warning:> This method is experimental and may change.
     
      @names = $dbh->tables( $catalog, $schema, $table, $type );
      @names = $dbh->tables;        # deprecated
     
    Simple interface to table_info(). Returns a list of matching
    table names, possibly including a catalog/schema prefix.
     
    See L</table_info> for a description of the parameters.
     
    If arguments are supplied then the table names are constructed and
    quoted by L</quote_identifier> to ensure they are usable even if
    they contain whitespace or reserved words etc. This is recommended
    (the "no-args means no-quoting" hack is only for historical reasons
    and will be changed in a later version).

The principle being that very few applications would be passing
parameters to tables() since that was only added in DBI 1.19
and very few drivers support it yet.

I really don't want to add an option to tables() to enable quoting
since that _really_ ought to be the default behaviour.

Comments welcome.

Tim.