virConnectGetCapabilities (third version) (was: Re: [Libvir] [PATCH] Add virConnectGetCapabilities call to return the capabilities of the driver / hypervisor)

Updated patch: I noticed that there was already a duplicate (and partial) version of virBuffer* in qemud/ code. The version I had is more complete so I changed the code to use that. I also renamed the files to "buf.c" and "buf.h" to be more consistent with the naming of the rest of the qemud/ code. Rich.