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/robust_ownership_tracker.cc b/aos/ipc_lib/robust_ownership_tracker.cc
index f106113..13edebc 100644
--- a/aos/ipc_lib/robust_ownership_tracker.cc
+++ b/aos/ipc_lib/robust_ownership_tracker.cc
@@ -2,8 +2,7 @@
 
 #include "aos/ipc_lib/lockless_queue.h"
 
-namespace aos {
-namespace ipc_lib {
+namespace aos::ipc_lib {
 
 ::std::string RobustOwnershipTracker::DebugString() const {
   ::std::stringstream s;
@@ -21,5 +20,4 @@
   return s.str();
 }
 
-}  // namespace ipc_lib
-}  // namespace aos
+}  // namespace aos::ipc_lib