add #ifdef guards around qd include
add #ifdef guards around qd include

fixes #136

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