Nest all namespaces

The compiler supports this now.  We can type less going forward.
No functional changes.

Signed-off-by: Stephan Pleines <pleines.stephan@gmail.com>
Change-Id: I29d6fa4f9aacc0e381f1a7637294db0392466995
diff --git a/aos/ipc_lib/queue_racer.cc b/aos/ipc_lib/queue_racer.cc
index 27f3835..aa73f2b 100644
--- a/aos/ipc_lib/queue_racer.cc
+++ b/aos/ipc_lib/queue_racer.cc
@@ -8,8 +8,7 @@
 
 #include "aos/ipc_lib/event.h"
 
-namespace aos {
-namespace ipc_lib {
+namespace aos::ipc_lib {
 namespace {
 
 struct ThreadPlusCount {
@@ -428,5 +427,4 @@
   }
 }
 
-}  // namespace ipc_lib
-}  // namespace aos
+}  // namespace aos::ipc_lib