Merge pull request #17 from bob-wilson/swift-newtype-docfix

Cherry-pick fix for swift_newtype attribute doc from upstream-with-swift
diff --git a/include/clang/Basic/AttrDocs.td b/include/clang/Basic/AttrDocs.td
index b2cb5e0..1409d58 100644
--- a/include/clang/Basic/AttrDocs.td
+++ b/include/clang/Basic/AttrDocs.td
@@ -1820,6 +1820,7 @@
 
 def SwiftNewtypeDocs : Documentation {
   let Category = SwiftDocs;
+  let Heading = "swift_newtype";
   let Content = [{
 The ``swift_newtype`` attribute indicates that the typedef to which the attribute appertains is imported as a new Swift type of the typedef's name.
 * ``swift_newtype(struct)`` means that a Swift struct will be created for this typedef.