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/buffered_solenoid.h b/frc971/wpilib/buffered_solenoid.h
index f0a4c11..1f127c5 100644
--- a/frc971/wpilib/buffered_solenoid.h
+++ b/frc971/wpilib/buffered_solenoid.h
@@ -1,8 +1,7 @@
 #ifndef FRC971_WPILIB_BUFFERED_SOLENOID_H_
 #define FRC971_WPILIB_BUFFERED_SOLENOID_H_
 
-namespace frc971 {
-namespace wpilib {
+namespace frc971::wpilib {
 
 class BufferedPcm;
 
@@ -22,7 +21,6 @@
   friend class BufferedPcm;
 };
 
-}  // namespace wpilib
-}  // namespace frc971
+}  // namespace frc971::wpilib
 
 #endif  // FRC971_WPILIB_BUFFERED_SOLENOID_H_