Completed 'cleanpackages' stage

Great script, exactly what i needed!

I noticed that these files were not removed by 'cleanpackages':
xcode_3.2.6_llvm-gcc4.2.pkg
Xcode107SDK.tar.gz
XcodePluginGCC42-Xcode4.tar.gz
XcodePluginGCC42.tar.gz
XcodePluginLLVMGCC42.tar.gz

I also added mention of SDK 10.7 to ‘usage’. Hope that's useful.