swift234

Add a module name field to code completion results

For decls, we get the most specific submodule from clang modules.  For
macros, we don't yet have a way to get this information, since the
mapping from module ID to submodule is burried in the ClangImporter.
Having submodule information for macros would also help reduce the space
cost of storing the module names, since we would hit the single-element
module name cache more often.

There is no special handling of imported headers, which currently come
through with their internal clang module name '__ObjC'.  Possibly these
should be treated as part of the current module.

A future commit will add the module name to swift-ide-test's output and update
the tests.

Swift SVN r26260