swift234

[ClangImporter] Remap factory methods according to the swift_name attr.

On a factory method, swift_name can have two effects:

- If the custom name has a base name of "init", import the method as an
  initializer, even if it doesn't follow the usual naming conventions.
- Otherwise, import the method as a method, even if it /would have/ been
  imported as an initializer.

There's a bit of trickiness around NSError**: currently you have to specify
the name of the error parameter on the Clang side even if it's going to be
deleted on the Swift side. We may want to change this later.

The test cases here exposed the issues in the previous two commits,
so this effectively depends on those for passing tests.

More of rdar://problem/19240897.

Swift SVN r28979