Support GCC 4.7

Removed constructors inheritance.
Removed emplace use.

Change-Id: I45224e3232d39ff22f758c7e387be2c9aff5eae0
Reviewed-on: https://weave-review.googlesource.com/1606
Reviewed-by: Vitaly Buka <vitalybuka@google.com>
diff --git a/examples/provider/event_task_runner.cc b/examples/provider/event_task_runner.cc
index c07e912..1d94612 100644
--- a/examples/provider/event_task_runner.cc
+++ b/examples/provider/event_task_runner.cc
@@ -34,7 +34,8 @@
   flags |= (what & kClosed) ? EV_CLOSED : 0;
   event* ioevent = event_new(base_.get(), fd, flags, FdEventHandler, this);
   EventPtr<event> ioeventPtr{ioevent};
-  fd_task_map_.emplace(fd, std::make_pair(std::move(ioeventPtr), task));
+  fd_task_map_.insert(
+      std::make_pair(fd, std::make_pair(std::move(ioeventPtr), task)));
   event_add(ioevent, nullptr);
 }