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/Sema/SemaExprObjC.cpp b/lib/Sema/SemaExprObjC.cpp
index 04aa455..9b33b1e 100644
--- a/lib/Sema/SemaExprObjC.cpp
+++ b/lib/Sema/SemaExprObjC.cpp
@@ -43,7 +43,7 @@
   // If we have a multi-part string, merge it all together.
   if (NumStrings != 1) {
     // Concatenate objc strings.
-    llvm::SmallString<128> StrBuf;
+    SmallString<128> StrBuf;
     SmallVector<SourceLocation, 8> StrLocs;
 
     for (unsigned i = 0; i != NumStrings; ++i) {