Fix backport of quadrant segment computation

git-svn-id: http://svn.osgeo.org/postgis/branches/2.0@11799 b70326c6-7e19-0410-871a-916f4a2858ee
lw_segment_side may return any negative number, not just -1 (#2420)

Adds other unit tests for cases exposing the bug (only exposing
in 2.0, maybe for lw_segment_side having changed implementation?)

git-svn-id: http://svn.osgeo.org/postgis/branches/2.0@11800 b70326c6-7e19-0410-871a-916f4a2858ee