COMP: Fix GCC warnings in ITK proxTV build#1

hjmjohnson wants to merge 3 commits into

InsightSoftwareConsortium:for/itk-proxtv-3.3.0-69062fe5InsightSoftwareConsortium/proxTV:for/itk-proxtv-3.3.0-69062fe5from

hjmjohnson:warnings-cleanup-gcchjmjohnson/proxTV:warnings-cleanup-gccCopy head branch name to clipboard