[MEDIUM] implement a monotonic internal clock

If the system date is set backwards while haproxy is running,
some scheduled events are delayed by the amount of time the
clock went backwards. This is particularly problematic on
systems where the date is set at boot, because it seldom
happens that health-checks do not get sent for a few hours.

Before switching to use clock_gettime() on systems which
provide it, we can at least ensure that the clock is not
going backwards and maintain two clocks : the "date" which
represents what the user wants to see (mostly for logs),
and an internal date stored in "now", used for scheduled
events.
diff --git a/src/client.c b/src/client.c
index 1dd318f..06a8ce1 100644
--- a/src/client.c
+++ b/src/client.c
@@ -1,7 +1,7 @@
 /*
  * Client-side variables and functions.
  *
- * Copyright 2000-2007 Willy Tarreau <w@1wt.eu>
+ * Copyright 2000-2008 Willy Tarreau <w@1wt.eu>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -201,7 +201,8 @@
 		else
 			s->logs.logwait = p->to_log;
 
-		s->logs.tv_accept = now;
+		s->logs.accept_date = date; /* user-visible date for logging */
+		s->logs.tv_accept = now;  /* corrected date for internal use */
 		tv_zero(&s->logs.tv_request);
 		s->logs.t_queue = -1;
 		s->logs.t_connect = -1;