Refactored PHP bindings tests

Patch by Benjamin Morel <benjamin.morel@gmail.com>

git-svn-id: http://svn.osgeo.org/geos/trunk@4016 5242fede-7e19-0410-aef8-94bd7d2200fb
OverlayOp: restrict intersection computations to the target extent

Speeds up INTERSECTION and DIFFERENCE operations between geometries
with small bounding box overlap.

git-svn-id: http://svn.osgeo.org/geos/trunk@4017 5242fede-7e19-0410-aef8-94bd7d2200fb
Further speedup difference/intersection at the validating phase

This avoids to insert to the output graph edges which do not intersect
the target envelope.

git-svn-id: http://svn.osgeo.org/geos/trunk@4018 5242fede-7e19-0410-aef8-94bd7d2200fb
Fixed compilation against thread-safe PHP (ZTS)

Closes #541
Patch-by: Benjamin Morel <benjamin.morel@gmail.com>
Signed-off-by: Sandro Santilli <strk@keybit.net>

git-svn-id: http://svn.osgeo.org/geos/trunk@4019 5242fede-7e19-0410-aef8-94bd7d2200fb
Allow GeometryGraph to get a restricting extent argument