swift234

[PrintAsObjC] Hack: Assume all option sets have typedefs. (#3961)

...because otherwise option sets that get imported as members using
NS_SWIFT_NAME are printed with an 'enum' tag, and the definition of
NS_OPTIONS only declares the typedef under C++.

We should come back and figure out something more principled for this
later, but for now this solves an issue with generated headers
imported into C++ translation units.

rdar://problem/27130343
(cherry picked from commit 02d25178669dc2dee3dd17ad024cc91d531822d3)