This bug fixes two issues:
* Overlap detection seems to be approximate and
  doesn't work for rotated text. Added a workaround
  for labels rotated at angles 45-135 and 225-315.

* Auto rotate labels, which overlap. This is done
  only for labels having zero degrees rotate.
  For forcing angles, use 'enable overlap' or
  non-zero angles (1 degree).
  Of course, zero degrees plus skipping of labels
  would no longer occur. Better solutions?