Tests importing AppKit have a tendency to be flaky when they share a
module cache with other builds using a different set of framework search
flags. Make sure they use a local cache, otherwise the compiler can
reuse incompatible cached modules.
Alternatively, we could align all builds using the same cache to have
exactly the same framework search paths or enable explicit module
builds. I picked the module cache as it's the most reliable solution in
the short and long term.
rdar://142949965
Completely mechanical changes:
- Explicit @objc in a few places
- Some imported APIs changed
- For the mix-and-match tests, just test version 4/5 instead of 3/4
We can't reliably reject raw values in an NS_ENUM's init(rawValue:), because the enum may have SPI or future values we don't statically know about. Fixes https://twitter.com/autorelease/status/524698585406124033
Swift SVN r23817
