Update third_party/protobuf to protobuf-v3.0.0-beta-3

third_party/protobuf/objectivec/GPBRuntimeTypes.h

Index: third_party/protobuf/objectivec/GPBRuntimeTypes.h
diff --git a/third_party/protobuf/objectivec/GPBRuntimeTypes.h b/third_party/protobuf/objectivec/GPBRuntimeTypes.h
index e91d86a647738ec91b3b3d10cf3c6ee5422ae5ed..0a38b110c6664c1eae9ca3a1f28b5c959a0e3fbe 100644
--- a/third_party/protobuf/objectivec/GPBRuntimeTypes.h
+++ b/third_party/protobuf/objectivec/GPBRuntimeTypes.h
@@ -67,7 +67,7 @@ typedef union {
 
 // Do not change the order of this enum (or add things to it) without thinking
 // about it very carefully. There are several things that depend on the order.
-typedef enum {
+typedef NS_ENUM(uint8_t, GPBDataType) {
   GPBDataTypeBool = 0,
   GPBDataTypeFixed32,
   GPBDataTypeSFixed32,
@@ -86,7 +86,7 @@ typedef enum {
   GPBDataTypeMessage,
   GPBDataTypeGroup,
   GPBDataTypeEnum,
-} GPBDataType;
+};
 
 enum {
   // A count of the number of types in GPBDataType. Separated out from the