[bug 0.7.0rc1] Makefile + xargs errors

[Jari Aalto]

The following lines:

    ./Makefile:13:  -find . -name "*.pyc" | xargs rm
    ./Makefile:14:  -find . -name "*.pyo" | xargs rm

Give nasty warnigns, when no *.pyc files are found. Under Linux/Cygwin
this could be fixed by adding --no-run-if-empty to xargs(1) call.

1) Supress warning messages
2) Those separate calls are unnecessary

   -find . -name "*.pyc" -o -name "*.pyo" | xargs rm > /dev/null 2>&1

Jari