this drops another static binary and replaces it with a very small
shell^Wpython script (again, python used to avoid sed / grep
implementation differences)

src/openscad.cc code was copy/pasted from .csg section; some refactoring
might make things nicer, but i didn't dare change too much for lack of
language knowledge

the echotest and dumptest still contain hacks to keep the delta to the
original unit tests minimal; possibly, some of these changes will make
it into the openscad program, at which time they can go away from there.