Ensure that UTF-8 works if TERM contains it.

Some people like to have their terminals claim UTF-8 support when
their terminals actually are set to another encoding. As nobody
appears to understand this, I have made a change to automatically
fix the encoding problems if possible. This uses ISO 2022 sequences
in order to dynamically change the encoding.

Fixes #692. Fixes #895. Fixes possible future issues about this.