BUG: disable ipa-cp-clone in GDCM

The ipa-cp-clone optimization with GCC 4.8 is causing GDCM to fail to
read pixel data. This optimization is disabled just for GDCM
libraries.

This patch addresses JIRA issue ITK-3237.

Change-Id: I1ecdf8e88a5860aefffe1faf97e632b1f678a4cf
Merge topic 'ITK-3237_GDCMInitializeFailureWithOptimizationFlag'

754278cb BUG: disable ipa-cp-clone in GDCM