updated oracle-cert.cer for VirtualBox 4.3.8

Creating base boxes with VirtualBox 4.3.8 does not install the vbox additions 4.3.8 silently. This is because the oracle-cert.cer file expired in February 2014, but still works installing vbox additions 4.3.6 even now.
The newer vbox additions 4.3.8 are signed in March 2014 and so the new oracle-cert.cer comes in for the silent install.
But how to make other users happy that still use VirtualBox 4.3.6 on their hosts, that could be tricky.
See also https://forums.virtualbox.org/viewtopic.php?f=1&t=60108 how to create the new oracle-cert.cer file from one of the newer vbox*.exe files.