REORG: time: move time-keeping code and variables to clock.c

There is currently a problem related to time keeping. We're mixing
the functions to perform calculations with the os-dependent code
needed to retrieve and adjust the local time.

This patch extracts from time.{c,h} the parts that are solely dedicated
to time keeping. These are the "now" or "before_poll" variables for
example, as well as the various now_*() functions that make use of
gettimeofday() and clock_gettime() to retrieve the current time.

The "tv_*" functions moved there were also more appropriately renamed
to "clock_*".

Other parts used to compute stolen time are in other files, they will
have to be picked next.
diff --git a/src/ev_kqueue.c b/src/ev_kqueue.c
index 3a53e07..df8eae2 100644
--- a/src/ev_kqueue.c
+++ b/src/ev_kqueue.c
@@ -19,12 +19,12 @@
 
 #include <haproxy/activity.h>
 #include <haproxy/api.h>
+#include <haproxy/clock.h>
 #include <haproxy/fd.h>
 #include <haproxy/global.h>
 #include <haproxy/signal.h>
 #include <haproxy/task.h>
 #include <haproxy/ticks.h>
-#include <haproxy/time.h>
 
 
 /* private data */
@@ -161,7 +161,7 @@
 		                kev,       // struct kevent *eventlist
 		                fd,        // int nevents
 		                &timeout_ts); // const struct timespec *timeout
-		tv_update_date(timeout, status);
+		clock_update_date(timeout, status);
 
 		if (status) {
 			activity[tid].poll_io++;