JShell: Consistent representation of unicode

Names expressed in Unicode are converted. Which, probably depending on locale, means they may be represented with '?' characters.

Should input match output? That is,

jshell> class \u00aa {}
| created class ?

jshell> class \u00ba extends \u00aa {}
| created class ?

Should this be:

jshell> class \u00aa {}
| created class \u00aa

jshell> class \u00ba extends \u00aa {}
| created class \u00ba

There is code in Eval in support of this (userReadableName()).