Make LongConstValueSource and TrieDateFieldSource classes public

In our custom request handler, we are boosting the query by decreasing recency of a document (thus implementing time bias). Solr provides BoostedQuery and ReciprocalFloatFunction classes that we use to implement time bias. But there are two classes, LongConstValueSource in org.apache.solr.search.ValueSourceParser, and TrieDateFieldSource in org.apache.solr.schema.TrieField, which are helpful in time bias implementation but which are defined as private.

Currently, we have made our own copies of these two classes. I wish you would make these two classes public in order for us to reuse them in our implementation of time bias functionality. I'm sure this would be beneficial to others, too.

Thank you.