COMP: Update teem to allow configuration with CMake < 2.8.12.1

Thanks to the following community members for their investigation and
issue reports:
Anderle, Kristjan <K.Anderle@gsi.de>
Andras Lasso <lasso@queensu.ca>
Sharp, Gregory C. <GCSHARP@mgh.harvard.edu>
Steve Pieper <pieper@isomics.com>
Csaba Pinter <csaba.pinter@queensu.ca>
Matthew Woehlke <matthew.woehlke@kitware.com>
Christopher Mullins <christopher.mullins@kitware.com>

// ------------------
Author: Jean-Christophe Fillion-Robin <jchris.fillionr@kitware.com>
Date: Fri Jan 30 22:00:50 2015 -0500

COMP: Prevent target double inclusion with older version of CMake

This commit fixes a regression introduced by Slicer/teem@e590e60c
(COMP: Build/Install modernization) where "export(TARGETS tee, ...)"
call has been introduced.

With older version of CMake, the generated target file didn't have the
multiple inclusion safe guard. Since this feature has been introduced
in CMake < 2.8.12.1 [1], this commit removes the existing
test and add a valid multiple inclusion guard.

[1] http://slicer-devel.65872.n3.nabble.com/Problems-with-building-Slicer-tp4033327p4033330.html

// ------------------

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23936 3bd1e089-480b-0410-8dfb-8563597acbee