Changed those two methods to only compile/link if necessary (according
to simplistic timestamp checks).
Added 'output_dir' to 'object_filenames()' and 'shared_object_filename()'.
now provided (minus the leading underscore) by the ccompiler module.
Fix 'compile()' to return the list of object files generated.
Cosmetic tweaks/delete cruft.
Added 'verbose' and 'dry_run' parameters to constructor.
Changed 'compile()', 'link_*()' to default lists arguments to None
rather than empty list.
Added implementations of the filename-mangling methods mandated by
the CCompiler interface.
Greg Ward