I had it in another repo, but now that the things are working better to start compacting the repos

   the VME_Wb interface has an additional register for controlling
   the msi interrupts. The rest of the changes in the VME bus and top
   file are for backwards compatibility. Now the user can synthesize
   for legacy interrupts or msi.

msi_interrupts: add MSI support to VME core. Now the src of an interrupt can be from another module (legacy interrupt) or from the MSI WB bus

Signed-off-by: Cesar Prados <c.prados@gsi.de>

       in the first commit is missing:
        doc folder
        cards example
        wishbone MSI interrupt