bind/unbind scalar symbol in scalar_vis instead of scalar_new
This way scalar events continue to work if the user happens to
change the [struct] arguments on us.

code for this is ugly (i.e., repetitive) and can probably be easily abstracted/refactored...

Make it possible to just send new attributes to GUI for [drawpolygon] and friends when a field value changes
(This performs better than erasing and redrawing the scalar in the GUI)

do a proper loadbang for canvas fields (needs more testing)

*added outlet to [draw] to notify for events
*added svg-style event mousedown (more to come)
*added a "drag" event for convenience (similar to curve_motion)
*fixed default strokelinejoin per svg spec
*event "bubbling" so that the closest shape to front gets the notification
*added "bbox" method to turn off bbox calculation (similar to curve's -n flag)
*added a "pointerevents" method per svg-spec
*fixed skewx and skewy transforms to use degrees instead of radians

*reversed "fix" to a regression made in a previous commit (see commit 28b0256f) and removed the old commit that caused the regression in the first place.

*added getscroll after redrawing gop and scalars that have been changed via properties dialog in case their xy positions changed

keep [drawsymbol] and [drawnumber] from flipping with negative gop scaling
default to black fill and no stroke, per svg spec
merged transform gui updates with other attributes
fixed tags so that array elements display properly