swift234

stdlib: Mark many higher-order function interfaces as 'rethrows'.

This covers:

- Lifetime-extending wrappers, like withExtendedLifetime, withCString, and withUnsafe*Pointer
- 'map' and friends on Optional
- 'indexOf'

A few APIs I haven't gotten to yet in this first pass:

- Autoclosure APIs, like assert, &&, etc.
- the 'isOrderedBefore' predicate for sorting APIs. The sorting implementation does some microoptimizations with 'inout' closures that violate rethrows checking.
- Strict 'map', 'filter', and friends on CollectionType. These need some plumbing in Lazy to be able to thread a Result-forming transformation through.

Swift SVN r30597