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/ipc_lib/signalfd.h b/aos/ipc_lib/signalfd.h
index a6991de..014ad5c 100644
--- a/aos/ipc_lib/signalfd.h
+++ b/aos/ipc_lib/signalfd.h
@@ -6,8 +6,7 @@
 
 #include <initializer_list>
 
-namespace aos {
-namespace ipc_lib {
+namespace aos::ipc_lib {
 
 // Class to manage a signalfd.
 class SignalFd {
@@ -34,7 +33,6 @@
   sigset_t blocked_mask_;
 };
 
-}  // namespace ipc_lib
-}  // namespace aos
+}  // namespace aos::ipc_lib
 
 #endif  // AOS_IPC_LIB_SIGNALFD_H_