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.)

llvm-svn: 149799
diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index bb0ae84..6b92b0a 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -6966,7 +6966,7 @@
     for (int i = FTI.NumArgs; i != 0; /* decrement in loop */) {
       --i;
       if (FTI.ArgInfo[i].Param == 0) {
-        llvm::SmallString<256> Code;
+        SmallString<256> Code;
         llvm::raw_svector_ostream(Code) << "  int "
                                         << FTI.ArgInfo[i].Ident->getName()
                                         << ";\n";