- most importantly, when the text changes and we set the buffer (as
happens when undoing), block the "changed" signal on the *buffer*
and not on the proxy (which doesn't even have a "changed"
signal). This was apparently something that happened during the
on-canvas editor merging.
- don't update the proxy when the layout changes, that's the wrong way
around. Instead, update the layout whenever the proxy changes,
remove lots of calls to update_layout() from the text editor and let
the "changed" callback on the buffer do its job of updating
everything.
Feed them into the text editor's IM context and into the proxy text
view's key bindings. Fixes input methods (e.g. entering of unicode
sequences seems to work flawlessly now).
