bulk connection(<>) in the when statements?

[donggyukim]

Sometimes, we want to use the <> operators in the when statements like: io <> thisIo when(thatCond) { io <> thatIo }

However, the current Chisel doesn't support it, emitting reassignment errors. I tried to change 'assign' to 'procAssign' in the <> method of Bits, which doesn't compile referencechip.