Allow defining custom charnames to ordinals

Allow defining custom charnames to ordinals

This adds the ability of a user to create a custom alias that maps to a
numeric ordinal value, instead of an official Unicode name.

The number of hashes went up so that is better to refer to them by a
name than a number, so I renamed them.

Also, viacode will return any defined user's alias for an otherwise
unamed code point.

This change is principally so that private use characters can be named
so it is more convenient to use them in Perl.