This PR corrects a bug that caused implicit specializations not to be added for an individual definition declared as anything more specific than an occurrence definition. Such a definition gets an implicit specialization of Occurrences::Life, as required, but previously it did not get an implied specialization for the more specific kind of thing that it is. For example,

resulted in the error “Must directly or indirectly specialize Items::Item”, because it was not being given the necessary implicit specialization of Items::Item. (Note that this error was avoided in the common case of the individual item definition specializing another non-individual item definition that already specializes Items::Item,)

The bug was caused because, when an occurrence definition was an individual definition, the OccurrenceDefinitionAdapter added an implicit specialization to Life instead of the normal base definition, rather than in addition to it. This PR corrects that.