remove old compatibility APIs, use StringRef versions instead.

llvm-svn: 119935
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 68f8b53..9e3e077 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -1548,8 +1548,8 @@
 
       const char *FullFileNameStart = BlobStart + Record[3];
       const FileEntry *File
-        = PP->getFileManager().getFile(FullFileNameStart,
-                                     FullFileNameStart + (BlobLen - Record[3]),
+      = PP->getFileManager().getFile(llvm::StringRef(FullFileNameStart,
+                                                     BlobLen - Record[3]),
                                      FileSystemOpts);
 
       // FIXME: Stable encoding