Runes in Plan 9 were limited to the 16-bit BMP when I drew up
the RPC protocol between graphical programs and devdraw
a long time ago. Now that they can be 32-bit, use a 32-bit wire
encoding too. A new message number to avoid problems with
other clients (like 9fans.net/go).
Add keyboard shortcut alt : , for U+1F602, face with tears of joy,
to test that it all works.