Add code to convert Multipolygon to WKB.
Allow run_test.sh to run multiple tests specified on command line.
Refactoring of geometry factory code.

The introduction of multipolygon_polygon_start() and
multipolygon_polygon_finish() functions makes the code much clearer.
Move recursive helper functions into detail namespace.
Update includes and forward references.
Make a bunch of loop variables const.
Rename variable 'wn' to 'node_ref' (left over from renaming of WayNode).