When checking for duplicate member definitions, also verify that we do not have a member with the same name and argument list (previously, this allowed two same-name methods with different return types - ick.)
Treat 'op_XXX' methods as special names.
Exempt special names from the more aggressive duplicate member detection (this is necessary because of op_Explicit)
Fix GetEnumerator definition in List`1
Fix particular detail of List`1.GetEnumerator implementation
Fix HashSet having two GetEnumerator implementations
Fix a bug in GetEnumerator fallback and improve error message
Make TestPrologue work in test_runner.html