Add transliteration of Emojis.

Suggested by Colin Leroy-Mira <colin@colino.net> in
<https://savannah.gnu.org/bugs/index.php?64046>.

* lib/translit.def: Add transliterations from glibc's fix of
<https://sourceware.org/bugzilla/show_bug.cgi?id=30649>.
* NEWS: Mention it.