BUG: Update DCMTK to fix segment access via number in DcmSegmentation

Tested-by: Andriy Fedorov <fedorov@bwh.harvard.edu>

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commit commontk/DCMTK@f55f3c8
Author: Michael Onken <onken@open-connections.de>
Date: Tue Nov 3 13:33:23 2015 -0500

[PATCH] Fixed segment access via Segment Number.

Fixed segment access via Segment Number which now assumes that the first
Segment Number is not 0 as in the underlying vector, but starts with 1.

Thanks to Andrey Fedorov <andrey.fedorov@gmail.com> for the report.

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git-svn-id: http://svn.slicer.org/Slicer4/trunk@24693 3bd1e089-480b-0410-8dfb-8563597acbee