perf session: Sort all events if ordered_samples=true

Now that we have timestamps on FORK, EXIT, COMM, MMAP events we can
sort everything in time order. This fixes the following observed
problem:

mmap(file1) -> pagefault() -> munmap(file1)
mmap(file2) -> pagefault() -> munmap(file2)

Resulted in decoding both pagefaults in file2 because the file1 map
was already replaced by the file2 map when the map address was
identical.

With all events sorted we decode both pagefaults correctly.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ian Munsie <imunsie@au1.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
LKML-Reference: <alpine.LFD.2.00.1012051220450.2653@localhost6.localdomain6>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>