It didn't, because the bitcode format said we only needed 8 possible
kinds of record within this block, which was a lie when both of these
flags were passed.
This is a backwards-compatible change, so no need to update the module
format version number.
From the Swift documentation:
"If you define an optional variable without providing a default value,
the variable is automatically set to nil for you."
This flag indicates that internal APIs within the module should be made
available to client code for testing purposes. Currently does nothing.
Not ready for developer consumption yet, ergo a hidden frontend-only flag.
Part of testability (rdar://problem/17732115)
Swift SVN r26292