describe-char should display the character's Unicode name

[Ted Zlatanov]

`describe-char' currently displays the character, but in cases where the
font is not capable of that, just the codepoint number is not very
useful for the user.  The character's Unicode name would be nice, but
the user has to customize `describe-char-unidata-list'.  At least the
Unicode name ('name) should be in `describe-char-unidata-list' by
default.  Since `describe-char' is used rarely and the user really wants
to know about the character, I think this is sensible.  It could also be
used for `what-cursor-position' which is similarly rarely used.

Ted