ftrace: add tracepoint for timer event

Hi,

We can monitor timer's lifecycle and behaviors by these tracepoint. 

Following tracepoints are introduced as ingo's suggestion in
	http://marc.info/?l=linux-kernel&m=123791899529128&...

for timer:
trace_timer_init()
trace_timer_start()
trace_timer_expire()
trace_timer_cancel()

for hrtimer:
trace_hrtimer_init()
trace_hrtimer_start()
trace_hrtimer_expire()
trace_hrtimer_cancel()

for itimer:
itimer_state
itimer_expire()

Changlog from latest patchset:
1: ours patches are base on Anton Blanchard's patch which can been found
   at:
   	http://marc.info/?l=linux-kernel&m=124331396919301&...
   but this patch is can't apply on Ingo's tip tree, so we rebase this
   patch against latest tip tree

2: fix those patches address Thomas's comment
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