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/aos/util/trapezoid_profile.cc b/aos/util/trapezoid_profile.cc
index e74110f..938ca75 100644
--- a/aos/util/trapezoid_profile.cc
+++ b/aos/util/trapezoid_profile.cc
@@ -4,8 +4,7 @@
 
 using ::Eigen::Matrix;
 
-namespace aos {
-namespace util {
+namespace aos::util {
 
 TrapezoidProfile::TrapezoidProfile(::std::chrono::nanoseconds delta_time)
     : maximum_acceleration_(0), maximum_velocity_(0), timestep_(delta_time) {
@@ -118,5 +117,4 @@
   deceleration_time_ = (goal_velocity - top_velocity) / deceleration_;
 }
 
-}  // namespace util
-}  // namespace aos
+}  // namespace aos::util