VNC client/server clipboard: Use Latin1 encoding

This patch fixes copy/paste between client and server of latin
characters using 8 bits. Characters needing more than one byte
cannot be copied due to a VNC protocol limitation.

The VNC (RFB) protocol does not support clipboard operations between
client and server using UTF-8, only ISO-8859-1 (Latin1).

Test: Copy/paste some latin characters with accents, umlauts, etc.
between client and server.