[src/dpe.h] more fix for deprecated finite()
[src/dpe.h] more fix for deprecated finite()

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