improve test_qios for timeval

The point is to show:

 * how slow it can be
 * that oveflow when summing two unnormalized timevals is not dealt
   with.

Change-Id: I0cc159613edfe55516eaa8999f89bfd42178cd5d
Reviewed-on: http://gerrit.aldebaran.lan/30027
Reviewed-by: cgestes <gestes@aldebaran-robotics.com>
Reviewed-by: sdalibard <sdalibard@aldebaran-robotics.com>
Reviewed-by: sbarthelemy <sbarthelemy@aldebaran-robotics.com>
Tested-by: sbarthelemy <sbarthelemy@aldebaran-robotics.com>
Reviewed-on: http://gerrit.aldebaran.lan/30173
qios: improve efficiency of timeval

Change-Id: I37f4ade2149037f73a3819ac91d479e16ad18605
Reviewed-on: http://gerrit.aldebaran.lan/30028
Reviewed-by: cgestes <gestes@aldebaran-robotics.com>
Reviewed-by: sdalibard <sdalibard@aldebaran-robotics.com>
Reviewed-by: ccollette <ccollette@aldebaran-robotics.com>
Reviewed-by: sbarthelemy <sbarthelemy@aldebaran-robotics.com>
Tested-by: sbarthelemy <sbarthelemy@aldebaran-robotics.com>
Reviewed-on: http://gerrit.aldebaran.lan/30174