PPCallbacks: Add hook for reaching the end of the main file, and fix DependencyFile to not do work in its destructor.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@99257 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Lex/PPLexerChange.cpp b/lib/Lex/PPLexerChange.cpp
index 6d1c132..335d3db 100644
--- a/lib/Lex/PPLexerChange.cpp
+++ b/lib/Lex/PPLexerChange.cpp
@@ -255,6 +255,7 @@
       if (!I->second->isUsed())
         Diag(I->second->getDefinitionLoc(), diag::pp_macro_not_used);
   }
+
   return true;
 }