Currently PrivateNames are tracked in 2 places in SymbolTables --- One in the ordinary symbol hash, and also separately in a list specifically for PrivateNames. This is used to provide DirectEval with information it needs regarding valid PrivateNames, however currently this is done whether an eval is known to occur or not. The information could potentially be useful for other things, like Web Inspector diagnostics, and such. We should investigate how worthwhile it is to have a separate hashset for this, as opposed to collecting private symbols from the main hash instead.