Revert Decl's iterators back to pointer value_type rather than reference value_type

In addition, I've made the pointer and reference typedef 'void' rather than T*
just so they can't get misused. I would've omitted them entirely but
std::distance likes them to be there even if it doesn't use them.

This rolls back r155808 and r155869.

Review by Doug Gregor incorporating feedback from Chandler Carruth.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@158104 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Analysis/CFG.cpp b/lib/Analysis/CFG.cpp
index 44a0eec..9ac92dc 100644
--- a/lib/Analysis/CFG.cpp
+++ b/lib/Analysis/CFG.cpp
@@ -832,7 +832,7 @@
     if (const CXXRecordDecl *CD = QT->getAsCXXRecordDecl())
       if (!CD->hasTrivialDestructor()) {
         autoCreateBlock();
-        appendMemberDtor(Block, &*FI);
+        appendMemberDtor(Block, *FI);
       }
   }
 }