alias resolver to the core java nio version with a better charset
database;
rather than falling back to not showing the user a failing message, fall
back to showing the user the message as ascii -- it makes it possible
to get _something_ out of an unknown-charset message, rather than just a
"ha ha. no." error.
Based on this comment in MIME4J, this seems like a win:
* Utility class for working with character sets. It is somewhat similar to
* the Java 1.4 <code>java.nio.charset.Charset</code> class but knows many
* more aliases and is compatible with Java 1.3. It will use a simple detection
* mechanism to detect what character sets the current VM supports. This will
* be a sub-set of the character sets listed in the
* <a href="http://java.sun.com/j2se/1.5.0/docs/guide/intl/encoding.doc.html">
* Java 1.5 (J2SE5.0) Supported Encodings</a> document.
* <p>
* The <a href="http://www.iana.org/assignments/character-sets">
* IANA Character Sets</a> document has been used to determine the preferred
* MIME character set names and to get a list of known aliases.
* <p>
