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/util/phased_loop.cc b/aos/util/phased_loop.cc
index 1f61775..476cc3f 100644
--- a/aos/util/phased_loop.cc
+++ b/aos/util/phased_loop.cc
@@ -2,8 +2,7 @@
 
 #include "glog/logging.h"
 
-namespace aos {
-namespace time {
+namespace aos::time {
 
 PhasedLoop::PhasedLoop(const monotonic_clock::duration interval,
                        const monotonic_clock::time_point monotonic_now,
@@ -79,5 +78,4 @@
   return result;
 }
 
-}  // namespace time
-}  // namespace aos
+}  // namespace aos::time