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/print/itm.cc b/motors/print/itm.cc
index 7f472c0..be657bc 100644
--- a/motors/print/itm.cc
+++ b/motors/print/itm.cc
@@ -6,8 +6,7 @@
 
 #include "motors/core/itm.h"
 
-namespace frc971 {
-namespace motors {
+namespace frc971::motors {
 namespace {
 
 template <int kPort>
@@ -96,5 +95,4 @@
   return buffer.size();
 }
 
-}  // namespace motors
-}  // namespace frc971
+}  // namespace frc971::motors