CastPP, CheckCastPP and Proj nodes are not "dead" loop safe after
the putback 20061023120554.jrose.dolphin-cleanups which added
new mmethods Ideal_allocation(), Ideal_klass(), Ideal_length().
These methods could bypass the nodes chain to get a klass or
an array's length from inputs of Allocation node:
Allocate <- Proj <- CheckCastPP.
As result dead data loop could be created.