drawin: Don't special-case moves

The code in drawin_moveresize() tries to be clever and only updates the drawing
state of the drawable when it is resized, not when it is moved around. This used
to be necessary because once upon a time, drawin_update_drawing() threw away all
of the drawing state and thus forcing a repaint. These days it just calls
drawable_set_geometry() as well and that function special-cases moves.

So this old code in drawin_moveresize() is no longer necessary and actually
caused problems.

These problems occurred because drawin_update_drawing() is being clever and
doesn't do anything for .visible = false drawins, because their drawing state
will be updated once they become visible. However, not skipping
drawable_set_geometry() means that this broke, because drawin_map() thought that
the drawing state was up to date while in reality it wasn't.

References: http://article.gmane.org/gmane.comp.window-managers.awesome/10852
Signed-off-by: Uli Schlachter <psychon@znc.in>
drawin_update_drawing: Remove optimization for invisible drawins

This fixes the following code:

   local d = drawin({})
   d.visible = true

The drawin now has a cairo surface assigned

   d.visible = false
   d.width = 1234
   d.visible = true

The width change while the drawin was not visible would not get propagated to
the drawable because of the code that this patch removes. The expectation was
that drawin_map() would update the drawable later.

However, because the drawin was already visible, its drawable also already has
a surface assigned. Thus, drawin_map() wouldn't update the drawable either.

Fix this by just removing this optimizations.

Signed-off-by: Uli Schlachter <psychon@znc.in>
wibox.layout.base.rect_to_device_geometry: Fix for "weird" rotations

The old code transformed the top-left and bottom-right corner of the rectangle
to device space and calculated a rectangle based on these two points. However,
if you rotate a rectangle by 45°, these two points will be directly above each
other and thus the old code would calculate a width of 0.

Fix this by transforming all four corners of the rectangle into device space and
calculating a rectangle based on this.

Signed-off-by: Uli Schlachter <psychon@znc.in>