run self-dual BKZ in at least dd precision
run self-dual BKZ in at least dd precision

fixes #170 and might possibly fixes #195

pfasante/fplll,fplll/fplll,shi-bai/fplll,shi-bai/fplll,gbonnoron/fplll,cr-marcstevens/fplll,pfasante/fplll,GottfriedHerold/fplll,blowfish880/fplll,blowfish880/fplll,cr-marcstevens/fplll,blowfish880/fplll,dstehle/fplll,pfasante/fplll,shi-bai/fplll,fplll/fplll,fplll/fplll,gbonnoron/fplll,shi-bai/fplll,cr-marcstevens/fplll,fplll/fplll,dstehle/fplll,GottfriedHerold/fplll,cr-marcstevens/fplll,GottfriedHerold/fplll,fplll/fplll,dstehle/fplll,gbonnoron/fplll