Make the preprocessor own its PPCallbacks, fixing a memory leak.
Patch by Sam Bishop!


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@48357 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Lex/Preprocessor.cpp b/Lex/Preprocessor.cpp
index 79b0d62..86156a0 100644
--- a/Lex/Preprocessor.cpp
+++ b/Lex/Preprocessor.cpp
@@ -109,6 +109,8 @@
 
   // Delete the scratch buffer info.
   delete ScratchBuf;
+
+  delete Callbacks;
 }
 
 /// Diag - Forwarding function for diagnostics.  This emits a diagnostic at