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/StaticAnalyzer/Checkers/UndefResultChecker.cpp b/lib/StaticAnalyzer/Checkers/UndefResultChecker.cpp
index c3cc2b5..3161a21 100644
--- a/lib/StaticAnalyzer/Checkers/UndefResultChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/UndefResultChecker.cpp
@@ -47,7 +47,7 @@
     if (!BT)
       BT.reset(new BuiltinBug("Result of operation is garbage or undefined"));
 
-    llvm::SmallString<256> sbuf;
+    SmallString<256> sbuf;
     llvm::raw_svector_ostream OS(sbuf);
     const Expr *Ex = NULL;
     bool isLeft = true;