Don't report an error when the VirtualBox registry key is missing,
as this just indicates that VirtualBox is not installed in general.

This matches the behavior of the XPCOM glue that silently ignores
a missing VBoxXPCOMC.so.

Add vboxArrayGetWithUintArg to handle new signature variations. Also
refactor vboxArrayGet* implementation to use a common helper function.

Deal with the incompatible changes in the VirtualBox 4.0 API. This
includes major changes in virtual machine and storage medium lookup,
in RDP server property handling, in session/lock handling and other
minor areas.

VirtualBox 4.0 also dropped the old event API and replaced it with a
completely new one. This is not fixed yet and will be addressed in
another patch. Therefore, currently the domain events are supported
for VirtualBox 3.x only.

Based on initial work from Jean-Baptiste Rouault.

Add a vboxArray to hide the details from the general driver code.

Don't require dlopen, but link to ole32 and oleaut32 on Windows.

Don't expose g_pVBoxFuncs anymore. It was only used to get the
version of the API. Make VBoxCGlueInit return the version instead.
This simplifies the implementation of the MSCOM glue layer.

Get the VirtualBox version from the registry.

Add a dummy implementation of the nsIEventQueue to the MSCOM glue
as there seems to be no direct equivalent with MSCOM. It might be
implemented using the normal window message loop. This requires
additional investigation.