Final clarification of BufferBuilder::bufferLineSingleSided behaviour (ticket #633)
* Ignore BufferParameters::setSingleSided() parameter as it is specific to areal geometries.
* Document semantic of input parameters.
* Document order of coordinates in generated output (conforms to PostGIS behaviour).
* Add test for coordinates order assumptions.

git-svn-id: http://svn.osgeo.org/geos/trunk@3823 5242fede-7e19-0410-aef8-94bd7d2200fb