Object used to store all informations for a single feature inheritance, because FEATURE_ACCUMULATOR is not able to specialize ANONYMOUS_FEATUREs (because not all FEATURE_STAMPs are ready).

The first step is to collect all informations for each anonymous feature of one type. Then the signatures may be resolved and the possible incompatibilities detected. The last step is to specialize assertions and body.

Those objects are recycled for the next type.