Add vtable anchor to classes.

llvm-svn: 350142
diff --git a/llvm/lib/Support/raw_ostream.cpp b/llvm/lib/Support/raw_ostream.cpp
index 81df38f..21dde7f 100644
--- a/llvm/lib/Support/raw_ostream.cpp
+++ b/llvm/lib/Support/raw_ostream.cpp
@@ -914,3 +914,5 @@
                                    uint64_t Offset) {}
 
 void raw_pwrite_stream::anchor() {}
+
+void buffer_ostream::anchor() {}