[Preprocessor] Remove PPMutationListener.

It's not used anymore.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178106 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/Preprocessor.cpp b/lib/Lex/Preprocessor.cpp
index bda72be..53c45dc 100644
--- a/lib/Lex/Preprocessor.cpp
+++ b/lib/Lex/Preprocessor.cpp
@@ -54,8 +54,6 @@
 //===----------------------------------------------------------------------===//
 ExternalPreprocessorSource::~ExternalPreprocessorSource() { }
 
-PPMutationListener::~PPMutationListener() { }
-
 Preprocessor::Preprocessor(IntrusiveRefCntPtr<PreprocessorOptions> PPOpts,
                            DiagnosticsEngine &diags, LangOptions &opts,
                            const TargetInfo *target, SourceManager &SM,
@@ -68,7 +66,7 @@
       Identifiers(opts, IILookup), IncrementalProcessing(IncrProcessing),
       CodeComplete(0), CodeCompletionFile(0), CodeCompletionOffset(0),
       CodeCompletionReached(0), SkipMainFilePreamble(0, true), CurPPLexer(0),
-      CurDirLookup(0), CurLexerKind(CLK_Lexer), Callbacks(0), Listener(0),
+      CurDirLookup(0), CurLexerKind(CLK_Lexer), Callbacks(0),
       MacroArgCache(0), Record(0), MIChainHead(0), MICache(0) {
   OwnsHeaderSearch = OwnsHeaders;