eina: Add a note about potential use of CLOCK_MONOTONIC

Note it down so we can think about this at some later point.

src/lib/eina/eina_inline_private.h

@@ -52,6 +52,9 @@ _eina_time_get(Eina_Nano_Time *tp)
    if (!clock_gettime(CLOCK_REALTIME, tp))
      return 0;
 # endif
+
+/* FIXME: Have a look if and how we can support CLOCK_MONOTONIC */
+
    struct timeval tv;
 
    if (gettimeofday(&tv, NULL))