householder.h: simple reformulation that avoids -DDEBUG compiler warning
householder.h: simple reformulation that avoids -DDEBUG compiler warning

fplll/fplll,dstehle/fplll,cr-marcstevens/fplll,dstehle/fplll,fplll/fplll,fplll/fplll,fplll/fplll,cr-marcstevens/fplll,fplll/fplll,cr-marcstevens/fplll,cr-marcstevens/fplll,dstehle/fplll