qi::Buffer: fix write size handling
qi::Buffer: fix write size handling

Change-Id: I6edf943792e6edcf0123aa0e115f420a37a46aa0
Reviewed-on: http://gerrit.aldebaran.lan:8080/466
Reviewed-by: llec <42f1a1c02cacc0f5b0188f0127ea77bedfdcf21a@aldebaran-robotics.com>
Tested-by: llec <42f1a1c02cacc0f5b0188f0127ea77bedfdcf21a@aldebaran-robotics.com>

aldebaran/libqi,aldebaran/libqi,aldebaran/libqi,vbarbaresi/libqi,aldebaran/libqi-java,aldebaran/libqi-java,bsautron/libqi,aldebaran/libqi-java