instead of clearing them.

Collector 952 (--with-python that has no trailing arg causes it to be passed to Python configurator, which raises an inscrutable error).

new comment block explains the cause and the cure.

        which is aware of extension classes that fill 'tp_callable'
        but don't define '__call__'.

      - Made KeywordIndex be more robust about receiving a value that
        is not a string or an iterable type.

Add an sdist target to the Makefile which builds a tarball source
distribution.

If the target version is not found, use the first "most acceptable" version found instead of the last.

a setup.py build_ext -i in order to prevent needing to needlessly rebuild
C extensions after a straight 'make' is performed.

Cleaned up makefile and added comments.

Also, moved mkzopeinstance and mkzeoinstance into 'utilities'.  It makes
more sense for 'bin' to be disposable in the face of inplace builds.

Change directories for build-tmp, build-lib, and build-scripts so they don't get copied to the install directory during 'make install'.

Also, change 'make clean' to remove '.so' files and not try to remove core files.