Add virtual dtor to PreprocessorLexer.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@59188 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Lex/PreprocessorLexer.h

@@ -60,6 +60,7 @@ protected:
   friend class Preprocessor;
   
   PreprocessorLexer() {}
+  virtual ~PreprocessorLexer();
   
   virtual void IndirectLex(Token& Result) = 0;
   

lib/Lex/PreprocessorLexer.cpp

@@ -18,6 +18,8 @@
 
 using namespace clang;
 
+PreprocessorLexer::~PreprocessorLexer() {}
+
 /// LexIncludeFilename - After the preprocessor has parsed a #include, lex and
 /// (potentially) macro expand the filename.
 void PreprocessorLexer::LexIncludeFilename(Token &FilenameTok) {