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/PPLexerChange.cpp b/lib/Lex/PPLexerChange.cpp
index 11c7870..3056e0c 100644
--- a/lib/Lex/PPLexerChange.cpp
+++ b/lib/Lex/PPLexerChange.cpp
@@ -206,7 +206,7 @@
 /// the given directory.
 static void computeRelativePath(FileManager &FM, const DirectoryEntry *Dir,
                                 const FileEntry *File,
-                                llvm::SmallString<128> &Result) {
+                                SmallString<128> &Result) {
   Result.clear();
 
   StringRef FilePath = File->getDir()->getName();
@@ -375,7 +375,7 @@
             if (!getSourceManager().hasFileInfo(Header)) {
               if (!ModMap.isHeaderInUnavailableModule(Header)) {
                 // Find the relative path that would access this header.
-                llvm::SmallString<128> RelativePath;
+                SmallString<128> RelativePath;
                 computeRelativePath(FileMgr, Dir, Header, RelativePath);              
                 Diag(StartLoc, diag::warn_uncovered_module_header)
                   << RelativePath;