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/DiagnosticRenderer.cpp b/lib/Frontend/DiagnosticRenderer.cpp
index 062b8a9..548a4a8 100644
--- a/lib/Frontend/DiagnosticRenderer.cpp
+++ b/lib/Frontend/DiagnosticRenderer.cpp
@@ -285,7 +285,7 @@
   if (Suppressed) {
     // Tell the user that we've skipped contexts.
     if (OnMacroInst == MacroSkipStart) {
-      llvm::SmallString<200> MessageStorage;
+      SmallString<200> MessageStorage;
       llvm::raw_svector_ostream Message(MessageStorage);
       Message << "(skipping " << (MacroSkipEnd - MacroSkipStart)
               << " expansions in backtrace; use -fmacro-backtrace-limit=0 to "
@@ -295,7 +295,7 @@
     return;
   }
   
-  llvm::SmallString<100> MessageStorage;
+  SmallString<100> MessageStorage;
   llvm::raw_svector_ostream Message(MessageStorage);
   Message << "expanded from macro '"
           << getImmediateMacroName(MacroLoc, SM, LangOpts) << "'";