This patch adds support for searching a buffer for Emojis without
needing to copy and paste them from another buffer or leaving isearch.
Isearch already provides some methods to search for non-ASCII
characters, so I decided to extend the package to search for Emoji as
well.

With this patch, during an incremental search, if you press 'C-x 8 e
RET', it will ask you for an Emoji character by name and insert it into
the search string.  A prefix argument N will insert N copies of the
character.

If you agree that this feature is sound and makes sense, please review
it and send me feedback or install it for me (I don't have commit
rights).  Perhaps a similar feature is also needed for query and
replace.

Thanks.