add numpy egg, as websockify (novnc core) requires it for new HyBi-10 WebSocket protocol (coming with Chrome 14 and Firefox 7)

Curl component was modified because of url not working. Changing it back
to original url.
This reverts commit 4cae8f81.

zc.buildout 1.5.3-dev-SlapOS-004 is not compatible with slapos.libnetworkcache.

It waits until defined file list is available.

Those extensions are only good in case of extremely complex profiles.

Sometimes O_CLOEXEC is not available.