Move a method from IdentifierTable.h out of line and remove the SmallString include.

Fix all the transitive include users.

llvm-svn: 149783
diff --git a/clang/lib/Basic/Builtins.cpp b/clang/lib/Basic/Builtins.cpp
index 7bdcdc6..c78a292 100644
--- a/clang/lib/Basic/Builtins.cpp
+++ b/clang/lib/Basic/Builtins.cpp
@@ -15,6 +15,7 @@
 #include "clang/Basic/IdentifierTable.h"
 #include "clang/Basic/TargetInfo.h"
 #include "clang/Basic/LangOptions.h"
+#include "llvm/ADT/SmallVector.h"
 using namespace clang;
 
 static const Builtin::Info BuiltinInfo[] = {