[BioC] Rgraphviz warnings in R-2.0

[Jeff Gentry]

> Warning messages:
> 1: Undefined slot classes in definition of "Ragraph":
> boundBox (class " boundingBox ") in:
> .completeClassSlots(ClassDef, where)
<snip other warnings>

These are from the order of the file collation but don't really have any
ill effect with the package usage.  There are actually quite a few
packages running around w/ these sorts of warnings, I fix them when I find
them.