Fix delay between receiving signal in separate thread and handling it

Also this allows increasing maximum wait time in poll(), though it
doesn't matter much

src/znc.cpp

@@ -243,8 +243,8 @@ void CZNC::Loop() {
         }
 
         // Csocket wants micro seconds
-        // 100 msec to 5 sec
-        m_Manager.DynamicSelectLoop(100 * 1000, 5 * 1000 * 1000);
+        // 100 msec to 5 min
+        m_Manager.DynamicSelectLoop(100 * 1000, 5 * 60 * 1000 * 1000);
     }
 }