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/Frontend/CreateInvocationFromCommandLine.cpp b/lib/Frontend/CreateInvocationFromCommandLine.cpp
index fec9b66..653da75 100644
--- a/lib/Frontend/CreateInvocationFromCommandLine.cpp
+++ b/lib/Frontend/CreateInvocationFromCommandLine.cpp
@@ -66,7 +66,7 @@
   // failed.
   const driver::JobList &Jobs = C->getJobs();
   if (Jobs.size() != 1 || !isa<driver::Command>(*Jobs.begin())) {
-    llvm::SmallString<256> Msg;
+    SmallString<256> Msg;
     llvm::raw_svector_ostream OS(Msg);
     C->PrintJob(OS, C->getJobs(), "; ", true);
     Diags->Report(diag::err_fe_expected_compiler_job) << OS.str();