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/logging/implementations.cc b/aos/logging/implementations.cc
index 3b4f905..da9e72b 100644
--- a/aos/logging/implementations.cc
+++ b/aos/logging/implementations.cc
@@ -8,8 +8,7 @@
 #include "aos/logging/printf_formats.h"
 #include "aos/time/time.h"
 
-namespace aos {
-namespace logging {
+namespace aos::logging {
 namespace internal {
 namespace {
 
@@ -83,5 +82,4 @@
   return context->implementation;
 }
 
-}  // namespace logging
-}  // namespace aos
+}  // namespace aos::logging