Constify argument of Preprocessor::getMacroInfoHistory and propagate to
callers, removing unneeded const_cast


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172372 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/PrintPreprocessedOutput.cpp b/lib/Frontend/PrintPreprocessedOutput.cpp
index 02da71b..cc8d935 100644
--- a/lib/Frontend/PrintPreprocessedOutput.cpp
+++ b/lib/Frontend/PrintPreprocessedOutput.cpp
@@ -565,7 +565,7 @@
   }
 }
 
-typedef std::pair<IdentifierInfo*, MacroInfo*> id_macro_pair;
+typedef std::pair<const IdentifierInfo *, MacroInfo *> id_macro_pair;
 static int MacroIDCompare(const void* a, const void* b) {
   const id_macro_pair *LHS = static_cast<const id_macro_pair*>(a);
   const id_macro_pair *RHS = static_cast<const id_macro_pair*>(b);