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/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp b/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
index 6175f9d..6d9ce0a 100644
--- a/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
+++ b/lib/StaticAnalyzer/Checkers/CallAndMessageChecker.cpp
@@ -143,8 +143,8 @@
           assert(RD && "Referred record has no definition");
           for (RecordDecl::field_iterator I =
                RD->field_begin(), E = RD->field_end(); I!=E; ++I) {
-            const FieldRegion *FR = MrMgr.getFieldRegion(&*I, R);
-            FieldChain.push_back(&*I);
+            const FieldRegion *FR = MrMgr.getFieldRegion(*I, R);
+            FieldChain.push_back(*I);
             T = I->getType();
             if (T->getAsStructureType()) {
               if (Find(FR))