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/gyro_interface.cc b/frc971/wpilib/gyro_interface.cc
index a90e95a..eb23b48 100644
--- a/frc971/wpilib/gyro_interface.cc
+++ b/frc971/wpilib/gyro_interface.cc
@@ -10,8 +10,7 @@
 #define M_PI 3.14159265358979323846
 #endif
 
-namespace frc971 {
-namespace wpilib {
+namespace frc971::wpilib {
 
 GyroInterface::GyroInterface() : gyro_(new frc::SPI(frc::SPI::kOnboardCS0)) {
   // The gyro goes up to 8.08MHz.
@@ -146,5 +145,4 @@
   return result;
 }
 
-}  // namespace wpilib
-}  // namespace frc971
+}  // namespace frc971::wpilib