no horiz canvas scroll over track-header automation fader
prepare support for [color] style name postfix
yet another button tweak..
special case track-header buttons
don't loose a redraw.

This more or less obsoletes the DisplaySuspender.
While RAII is nice, the DisplaySuspender cannot be
used from outside gtk2_ardour eg Mute/Solo signals
notifications from libardour (which don't originate
from the GUI).

The DisplaySuspender is still useful, because it
explicitly disables re-display and forces a single
expose at the end.
NOOP, re-indent, remove trailing whitespace, sort includes