Actually distinguish between RecordDecl::field_iterator and RecordDecl::field_const_iterator, propagating the constness down to the FieldDecls.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@60883 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Driver/RewriteBlocks.cpp b/Driver/RewriteBlocks.cpp
index 5b6e1a9..1e7a6af 100644
--- a/Driver/RewriteBlocks.cpp
+++ b/Driver/RewriteBlocks.cpp
@@ -1134,7 +1134,7 @@
   }
   if (RecordDecl *RD = dyn_cast<RecordDecl>(D)) {
     if (RD->isDefinition()) {
-      for (RecordDecl::field_const_iterator i = RD->field_begin(), 
+      for (RecordDecl::field_iterator i = RD->field_begin(), 
              e = RD->field_end(); i != e; ++i) {
         FieldDecl *FD = *i;
         if (isBlockPointerType(FD->getType()))