* Better error message for Union parsers that find something unexpected.
* A test showing that an optional parser accepts the same language as the original language, and also null input. (Name: Parsing-Derivatives-fbs.18
Author: fbs
Time: 25 April 2013, 5:22:49.73 pm
UUID: 655b7933-9f8d-4e34-a8d4-cb87f090263f
Ancestors: Parsing-Derivatives-fbs.17)