Please give back insighttoolkit

[Mathieu Malaterre <mathieu.malaterre@gmail.com>]

Please give back insighttoolkit. CMake 2.8.7 behavior changed from
2.8.6, and thus generated improper cmake export file for gdcm package.
See #664188 for refs.

gb insighttoolkit_3.20.1-5 . armhf i386 kfreebsd-amd64 kfreebsd-i386
powerpc s390x .

Thanks
--
Mathieu