initGEOS/finishGEOS and multiple subsystems

Recently, Steve Lime reconfigured MapServer to use the GEOS C API 
instead of the C++ one.  Python Cartographic Library, which builds on 
MapServer and GEOS, among other things, *also* uses the GEOS C 
API.  Each subsystem doesn't know when the other is calling 
initGEOS/finishGEOS, and on teardown, this is causing a segfault 
because the geomFactory has already been destroyed.

After some discussion on #gdal with Frank, Norman, and Mateusz, we 
suggest that initGEOS/finishGEOS do some reference counting to ensure 
that geomFactory isn't prematurely destroyed.

Does this seem reasonable?

Howard