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

clang/lib/Sema/CodeCompleteConsumer.cpp

@@ -260,7 +260,7 @@ const char *CodeCompletionAllocator::CopyString(Twine String) {
   // FIXME: It would be more efficient to teach Twine to tell us its size and
   // then add a routine there to fill in an allocated char* with the contents
   // of the string.
-  llvm::SmallString<128> Data;
+  SmallString<128> Data;
   return CopyString(String.toStringRef(Data));
 }