make timers best-effort non-drifting

ev++.h

@@ -46,6 +46,21 @@ namespace ev {
 
   #include "ev.h"
 
+  enum {
+    UNDEF    = EV_UNDEF,
+    NONE     = EV_NONE,
+    READ     = EV_READ,
+    WRITE    = EV_WRITE,
+    TIMEOUT  = EV_TIMEOUT,
+    PERIODIC = EV_PERIODIC,
+    SIGNAL   = EV_SIGNAL,
+    IDLE     = EV_IDLE,
+    CHECK    = EV_CHECK,
+    PREPARE  = EV_PREPARE,
+    CHILD    = EV_CHILD,
+    ERROR    = EV_ERROR,
+  };
+
   typedef ev_tstamp tstamp;
 
   inline ev_tstamp now (EV_P)

ev.c

@@ -1339,7 +1339,7 @@ ev_timer_stop (EV_P_ struct ev_timer *w)
       downheap ((WT *)timers, timercnt, ((W)w)->active - 1);
     }
 
-  ((WT)w)->at = w->repeat;
+  ((WT)w)->at -= mn_now;
 
   ev_stop (EV_A_ (W)w);
 }