Bug 920346 - Setting PYTHONPATH to original value even if original was blank.
Merge pull request #1256 from vinodc/pythonpath

Bug 920346 - Set PYTHONPATH to original value even if original was blank. r=Mossop
Bug 910647 sidebars no longer migrate across windows with different private states due to bug 885054
Merge branch 'master' of git://github.com/mozilla/addon-sdk into 910647