* Unify the capitalization across all user-visible error messages (fatal errors, assertion failures, precondition failures) produced by the runtime, standard library and the compiler.
* Update some more tests to the new expectations.
* Give Sequence a top-level Element, constrain Iterator to match
* Remove many instances of Iterator.
* Fixed various hard-coded tests
* XFAIL a few tests that need further investigation
* Change assoc type for arrayLiteralConvertible
* Mop up remaining "better expressed as a where clause" warnings
* Fix UnicodeDecoders prototype test
* Fix UIntBuffer
* Fix hard-coded Element identifier in CSDiag
* Fix up more tests
* Account for flatMap changes
Eliminate all of the redundant conformance constraints in the standard
library that were identified by the newly-introduced warning for
redundant, explicitly-specified conformances.