right now a None value that's passed through the compiler for literal_processor() is passed in, and none of the handlers expect None and just return None, where the compiler then renders nothing.

Changes should be as follows:

1. the compiler, when it sees the value is None, returns the string NULL or otherwise uses a render_null() method of some kind; it does not send the data to the literal_processor() for the type, unless should_evaluate_none on the type is set
2. all the types that have literal_processor() and do not have "should_evaluate_none" can assume the value passed is non None
3. tests for JSON/JSONB doing "evaluate none" style tests should be added; the base test_literal_round_trip() suite should do a NULL round trip for all datatypes

this could be a 2.0 thing or a 2.1 thing