fix - missing file in support for support for nspkg.pth-style namespaces

See htgoebel's commit 2cf7654e35 and his comment on ticket #502 at
http://www.pyinstaller.org/ticket/502
Merge pull request #130 from exvito/ticket-502-fix-nspkg.pth-style

Missing file in support for support for nspkg.pth-style namespaces
Add a comment to the fake-file required for nspkg.pth-style namespaces.