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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/aos_sync.cc b/aos/ipc_lib/aos_sync.cc
index 6bf5d8c..b1a9fb0 100644
--- a/aos/ipc_lib/aos_sync.cc
+++ b/aos/ipc_lib/aos_sync.cc
@@ -1054,9 +1054,7 @@
   return !__atomic_exchange_n(m, 0, __ATOMIC_SEQ_CST);
 }
 
-namespace aos {
-namespace linux_code {
-namespace ipc_lib {
+namespace aos::linux_code::ipc_lib {
 
 // Sets an extra offset between mutexes and the value we use for them in the
 // robust list (only the forward pointers). This is used to work around a kernel
@@ -1070,6 +1068,4 @@
 // This is mainly useful for testing.
 bool HaveLockedMutexes() { return my_robust_list::HaveLockedMutexes(); }
 
-}  // namespace ipc_lib
-}  // namespace linux_code
-}  // namespace aos
+}  // namespace aos::linux_code::ipc_lib