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/frc971/wpilib/joystick_sender.cc b/frc971/wpilib/joystick_sender.cc
index 26f7545..f3b97f6 100644
--- a/frc971/wpilib/joystick_sender.cc
+++ b/frc971/wpilib/joystick_sender.cc
@@ -8,8 +8,7 @@
 #include "frc971/wpilib/ahal/DriverStation.h"
 #include "hal/HAL.h"
 
-namespace frc971 {
-namespace wpilib {
+namespace frc971::wpilib {
 
 using aos::Joystick;
 
@@ -138,5 +137,4 @@
   });
 }
 
-}  // namespace wpilib
-}  // namespace frc971
+}  // namespace frc971::wpilib