Added nsAutoUpdateViewBatch class, and use it in
nsPlaintexteditor::Undo()/Redo().
editor/base/nsEditorUtils.h
editor/base/nsPlaintextEditor.cpp
r=jfrancis@netscape.comsr=sfraser@netscape.com
git-svn-id: svn://10.0.0.236/trunk@94654 18797224-902f-48f8-a5cc-f745e15eee43