Basic: import SmallString<> into clang namespace

(I was going to fix the TODO about DenseMap too, but
that would break self-host right now. See PR11922.)

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149799 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CodeGenTBAA.cpp b/lib/CodeGen/CodeGenTBAA.cpp
index 594c6c4..401ad10 100644
--- a/lib/CodeGen/CodeGenTBAA.cpp
+++ b/lib/CodeGen/CodeGenTBAA.cpp
@@ -170,7 +170,7 @@
 
     // TODO: This is using the RTTI name. Is there a better way to get
     // a unique string for a type?
-    llvm::SmallString<256> OutName;
+    SmallString<256> OutName;
     llvm::raw_svector_ostream Out(OutName);
     MContext.mangleCXXRTTIName(QualType(ETy, 0), Out);
     Out.flush();