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/Lex/PPMacroExpansion.cpp b/lib/Lex/PPMacroExpansion.cpp
index 8793ff5..3fe3ab3 100644
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@@ -776,7 +776,7 @@
   PP.getCurrentLexer()->LexIncludeFilename(Tok);
 
   // Reserve a buffer to get the spelling.
-  llvm::SmallString<128> FilenameBuffer;
+  SmallString<128> FilenameBuffer;
   StringRef Filename;
   SourceLocation EndLoc;
   
@@ -878,7 +878,7 @@
 
   ++NumBuiltinMacroExpanded;
 
-  llvm::SmallString<128> TmpBuffer;
+  SmallString<128> TmpBuffer;
   llvm::raw_svector_ostream OS(TmpBuffer);
 
   // Set up the return result.
@@ -925,7 +925,7 @@
     }
 
     // Escape this filename.  Turn '\' -> '\\' '"' -> '\"'
-    llvm::SmallString<128> FN;
+    SmallString<128> FN;
     if (PLoc.isValid()) {
       FN += PLoc.getFilename();
       Lexer::Stringify(FN);