Have ObjC use the new future-proofed C interface

src/objective-c/GRPCClient/private/GRPCCompletionQueue.m

@@ -43,7 +43,7 @@
 
 - (instancetype)init {
   if ((self = [super init])) {
-    _unmanagedQueue = grpc_completion_queue_create();
+    _unmanagedQueue = grpc_completion_queue_create(NULL);
 
     // This is for the following block to capture the pointer by value (instead
     // of retaining self and doing self->_unmanagedQueue). This is essential
@@ -64,7 +64,8 @@
       while (YES) {
         // The following call blocks until an event is available.
         grpc_event event = grpc_completion_queue_next(unmanagedQueue,
-                                                      gpr_inf_future(GPR_CLOCK_REALTIME));
+                                                      gpr_inf_future(GPR_CLOCK_REALTIME),
+                                                      NULL);
         GRPCQueueCompletionHandler handler;
         switch (event.type) {
           case GRPC_OP_COMPLETE:

src/objective-c/GRPCClient/private/GRPCHost.m

@@ -97,7 +97,7 @@
                                   queue.unmanagedQueue,
                                   path.UTF8String,
                                   self.hostName.UTF8String,
-                                  gpr_inf_future(GPR_CLOCK_REALTIME));
+                                  gpr_inf_future(GPR_CLOCK_REALTIME), NULL);
 }
 
 - (GRPCChannel *)channel {

src/objective-c/GRPCClient/private/GRPCUnsecuredChannel.m

@@ -38,7 +38,7 @@
 @implementation GRPCUnsecuredChannel
 
 - (instancetype)initWithHost:(NSString *)host {
-  return (self = [super initWithChannel:grpc_insecure_channel_create(host.UTF8String, NULL)]);
+  return (self = [super initWithChannel:grpc_insecure_channel_create(host.UTF8String, NULL, NULL)]);
 }
 
 // TODO(jcanizales): GRPCSecureChannel and GRPCUnsecuredChannel are just convenience initializers

src/objective-c/GRPCClient/private/GRPCWrappedCall.m

@@ -282,7 +282,7 @@
     for (GRPCOperation *operation in operations) {
       [operation finish];
     }
-  }));
+  }), NULL);
   gpr_free(ops_array);
 
   if (error != GRPC_CALL_OK) {
@@ -293,7 +293,7 @@
 }
 
 - (void)cancel {
-  grpc_call_cancel(_call);
+  grpc_call_cancel(_call, NULL);
 }
 
 - (void)dealloc {