Fix TopologyException in Raster Instersection

Raster _st_intersects was doing ST_Collect of polygons building each pixel,
which led to invalid geometry and TopologyException.

Thanks Vinícius A.B. Schmidt for reporting and testing solutions.

Closes #4132



git-svn-id: http://svn.osgeo.org/postgis/trunk@16660 b70326c6-7e19-0410-871a-916f4a2858ee
1 job for svn-trunk in 21 minutes and 47 seconds
Status Job ID Name Coverage
  Test
passed #83503223
test

00:21:47