Nest some more namespaces

Did someone previously suggest that all namespace had been
nested?  Silly.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I22278c1caaeba8b47dc46fb2ed3078c20a11e190
diff --git a/aos/events/epoll.h b/aos/events/epoll.h
index 2b7eb76..526c6a7 100644
--- a/aos/events/epoll.h
+++ b/aos/events/epoll.h
@@ -12,8 +12,7 @@
 
 #include "aos/time/time.h"
 
-namespace aos {
-namespace internal {
+namespace aos::internal {
 
 // Class wrapping up timerfd.
 class TimerFd {
@@ -187,7 +186,6 @@
   std::vector<std::function<void()>> before_epoll_wait_functions_;
 };
 
-}  // namespace internal
-}  // namespace aos
+}  // namespace aos::internal
 
 #endif  // AOS_EVENTS_EPOLL_H_