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/ItaniumCXXABI.cpp b/lib/CodeGen/ItaniumCXXABI.cpp
index b319420..1e5b2c2 100644
--- a/lib/CodeGen/ItaniumCXXABI.cpp
+++ b/lib/CodeGen/ItaniumCXXABI.cpp
@@ -1040,7 +1040,7 @@
   llvm::PointerType *GuardPtrTy = GuardTy->getPointerTo();
 
   // Create the guard variable.
-  llvm::SmallString<256> GuardVName;
+  SmallString<256> GuardVName;
   llvm::raw_svector_ostream Out(GuardVName);
   getMangleContext().mangleItaniumGuardVariable(&D, Out);
   Out.flush();