third_party/protobuf: Update to HEAD (83d681ee2c)

third_party/protobuf/objectivec/GPBUnknownField.m

Index: third_party/protobuf/objectivec/GPBUnknownField.m
diff --git a/third_party/protobuf/objectivec/GPBUnknownField.m b/third_party/protobuf/objectivec/GPBUnknownField.m
index 0e29bde50f66b5861d93a180fa36a5b5e1b85c37..30efe7563b712d61e6404b6597bd3dcfaffc64ed 100644
--- a/third_party/protobuf/objectivec/GPBUnknownField.m
+++ b/third_party/protobuf/objectivec/GPBUnknownField.m
@@ -67,6 +67,12 @@
   [super dealloc];
 }
 
+// Direct access is use for speed, to avoid even internally declaring things
+// read/write, etc. The warning is enabled in the project to ensure code calling
+// protos can turn on -Wdirect-ivar-access without issues.
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdirect-ivar-access"
+
 - (id)copyWithZone:(NSZone *)zone {
   GPBUnknownField *result =
       [[GPBUnknownField allocWithZone:zone] initWithNumber:number_];
@@ -323,4 +329,6 @@
   }
 }
 
+#pragma clang diagnostic pop
+
 @end