Use qiLogCategory in libqi

Change-Id: I8154dac1a78c141efb7a77152f74e4ff5d291c11
Reviewed-on: http://gerrit.aldebaran.lan:8080/15764
Reviewed-by: ncornu <ncornu@aldebaran-robotics.com>
Tested-by: ncornu <ncornu@aldebaran-robotics.com>
Replace _private by _p

Change-Id: Ib5f2e9abd1428e5fdddea9c891975d8307863797
Reviewed-on: http://gerrit.aldebaran.lan:8080/15797
Reviewed-by: cgestes <gestes@aldebaran-robotics.com>
Tested-by: ncornu <ncornu@aldebaran-robotics.com>