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/motors/peripheral/adc.cc b/motors/peripheral/adc.cc
index 64f1557..11a91ff 100644
--- a/motors/peripheral/adc.cc
+++ b/motors/peripheral/adc.cc
@@ -2,8 +2,7 @@
 
 #include "motors/core/kinetis.h"
 
-namespace frc971 {
-namespace motors {
+namespace frc971::motors {
 namespace {
 
 #define ADC_SC2_BASE \
@@ -58,5 +57,4 @@
   ADC_INIT_SINGLE(1, (adc1_channels == AdcChannels::kB) ? ADC_CFG2_MUXSEL : 0);
 }
 
-}  // namespace motors
-}  // namespace frc971
+}  // namespace frc971::motors