At some point I want to propose a revised model for exports, but for now
just mark that support for '@exported' is still experimental and subject
to change. (Thanks, Max.)
Introduce a number of small overlays to bridge the NSError domains for
a number of frameworks into existing imported enums. This batch only
covers cases where there is an existing NS_ENUM describing the codes
for the domain, so we need only extend that enum to provide the
appropriate _BridgedNSError conformance.
This is the bulk of rdar://problem/20536610.
Swift SVN r28585
