[bug] 0.7 Makefile fixes (clean target error suppression)

[Jari Aalto]

The discussion we had didnät carry into 0.7 :-) Correct these
to next release:

    ./setup.py clean
    running clean
    find . -name "*.pyc" | xargs rm
    rm: missing operand
    Try `rm --help' for more information.
    make: [clean] Error 123 (ignored)
    find . -name "*.pyo" | xargs rm
    rm: missing operand
    Try `rm --help' for more information.
    make: [clean] Error 123 (ignored)
    rm -rf test????.tmp
    make: *** No rule to make target `distclean'.  Stop.

The consensus was to add -f option:

    rm -f

Jari