This checkin adds the implementations for encoding
HTML and plain text:
nsTextEncoder::EncodeToString(..)
nsHTMLEncoder::EncodeToStream(..)
Hooked these services into the nsHTMLEditor implemenation
We probably want to update the clipboard code to
use the same pattern as in nsHTMLEditor.cpp
git-svn-id: svn://10.0.0.236/trunk@34518 18797224-902f-48f8-a5cc-f745e15eee43