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/Sema/SemaLambda.cpp b/lib/Sema/SemaLambda.cpp
index 51a44a9..f64be51 100644
--- a/lib/Sema/SemaLambda.cpp
+++ b/lib/Sema/SemaLambda.cpp
@@ -444,7 +444,7 @@
   SmallVector<Decl*, 4> Fields;
   for (RecordDecl::field_iterator i = Class->field_begin(),
                                   e = Class->field_end(); i != e; ++i)
-    Fields.push_back(&*i);
+    Fields.push_back(*i);
   ActOnFields(0, Class->getLocation(), Class, Fields, 
               SourceLocation(), SourceLocation(), 0);
   CheckCompletedCXXClass(Class);
@@ -690,7 +690,7 @@
     SmallVector<Decl*, 4> Fields;
     for (RecordDecl::field_iterator i = Class->field_begin(),
                                     e = Class->field_end(); i != e; ++i)
-    Fields.push_back(&*i);
+      Fields.push_back(*i);
     ActOnFields(0, Class->getLocation(), Class, Fields, 
                 SourceLocation(), SourceLocation(), 0);
     CheckCompletedCXXClass(Class);