Problem: thread name is redundant

Solution: call it simply "ZMQ background" instead of "ZMQ b/g thread"

src/ctx.cpp

@@ -412,7 +412,7 @@ void zmq::ctx_t::start_thread (thread_t &thread_, thread_fn *tfn_, void *arg_) c
 {
     thread_.start(tfn_, arg_);
     thread_.setSchedulingParameters(thread_priority, thread_sched_policy);
-    thread_.setThreadName ("ZMQ b/g thread");
+    thread_.setThreadName ("ZMQ background");
 }
 
 void zmq::ctx_t::send_command (uint32_t tid_, const command_t &command_)