time/delta_time: return nanoseconds objects rather than floats

time.cpp

@@ -46,13 +46,13 @@ delta_clock::delta_clock ():
 
 
 //-----------------------------------------------------------------------------
-float
+std::chrono::nanoseconds
-delta_clock::seconds (void)
+delta_clock::dt (void)
 {
     time.prev = time.curr;
     time.curr = nanoseconds ();
 
-    return (time.curr - time.prev) / static_cast<float> (SECOND);
+    return std::chrono::nanoseconds (time.curr - time.prev);
 }
 
 

time.hpp

@@ -46,7 +46,7 @@ namespace util {
     class delta_clock {
         public:
             delta_clock ();
-            float seconds (void);
+            std::chrono::nanoseconds dt(void);
 
         protected:
             struct {