debian: silence lintian hardening warning

W: antpm: hardening-no-fortify-functions usr/bin/antpm-downloader
W: antpm: hardening-no-fortify-functions usr/bin/antpm-fit2gpx
W: antpm: hardening-no-fortify-functions usr/bin/antpm-usbmon2ant

by using dpkg-buildflags
debian: make a copy of the changelog

as git-dch still makes mistakes