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/vision/events/tcp_client.cc b/aos/vision/events/tcp_client.cc
index 0a926db..65b646c 100644
--- a/aos/vision/events/tcp_client.cc
+++ b/aos/vision/events/tcp_client.cc
@@ -15,8 +15,7 @@
 
 #include "aos/logging/logging.h"
 
-namespace aos {
-namespace events {
+namespace aos::events {
 
 namespace {
 int MakeSocketNonBlocking(int sfd) {
@@ -63,5 +62,4 @@
 TcpClient::TcpClient(const std::string &hostname, int portno)
     : EpollEvent(OpenClient(hostname, portno)) {}
 
-}  // namespace events
-}  // namespace aos
+}  // namespace aos::events