Document methods, separate non-trivial implementations from declarations

- Also fix integer overflow issue in ticks_to_next_event

src/test/test_basic.cc

@@ -155,7 +155,8 @@ bool test_ticks_to_next_event() {
 
     // No timers scheduled, return the max value.
     EXPECT_INTEQ(timers.ticks_to_next_event(100), 100);
-    EXPECT_INTEQ(timers.ticks_to_next_event(0), 0);
+    EXPECT_INTEQ(timers.ticks_to_next_event(),
+                 std::numeric_limits<Tick>::max());
 
     for (int i = 0; i < 10; ++i) {
         // Just vanilla tests
@@ -204,6 +205,10 @@ bool test_ticks_to_next_event() {
         timers.advance(32);
     }
 
+    timer.cancel();
+    EXPECT_INTEQ(timers.ticks_to_next_event(),
+                 std::numeric_limits<Tick>::max());
+
     return true;
 }