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/index.cc b/aos/ipc_lib/index.cc
index 4701f51..b6796b6 100644
--- a/aos/ipc_lib/index.cc
+++ b/aos/ipc_lib/index.cc
@@ -3,8 +3,7 @@
 #include <sstream>
 #include <string>
 
-namespace aos {
-namespace ipc_lib {
+namespace aos::ipc_lib {
 
 ::std::string QueueIndex::DebugString() const {
   if (valid()) {
@@ -29,5 +28,4 @@
   }
 }
 
-}  // namespace ipc_lib
-}  // namespace aos
+}  // namespace aos::ipc_lib