BUG: fix integer overflow in special.spence
BUG: fix integer overflow in special.spence

Closes gh-6091.

matthewalbani/scipy,e-q/scipy,nonhermitian/scipy,mikebenfield/scipy,andyfaff/scipy,gdooper/scipy,rgommers/scipy,argriffing/scipy,sriki18/scipy,behzadnouri/scipy,Newman101/scipy,josephcslater/scipy,endolith/scipy,Stefan-Endres/scipy,pyramania/scipy,kleskjr/scipy,ilayn/scipy,woodscn/scipy,e-q/scipy,pizzathief/scipy,ilayn/scipy,jor-/scipy,person142/scipy,e-q/scipy,maniteja123/scipy,jor-/scipy,WarrenWeckesser/scipy,sriki18/scipy,haudren/scipy,aarchiba/scipy,kalvdans/scipy,Eric89GXL/scipy,Newman101/scipy,grlee77/scipy,mdhaber/scipy,tylerjereddy/scipy,matthewalbani/scipy,sriki18/scipy,vigna/scipy,josephcslater/scipy,aarchiba/scipy,nonhermitian/scipy,jjhelmus/scipy,aeklant/scipy,e-q/scipy,pyramania/scipy,dominicelse/scipy,surhudm/scipy,perimosocordiae/scipy,Eric89GXL/scipy,lhilt/scipy,tylerjereddy/scipy,pyramania/scipy,aarchiba/scipy,aarchiba/scipy,person142/scipy,josephcslater/scipy,argriffing/scipy,pschella/scipy,anielsen001/scipy,dominicelse/scipy,Newman101/scipy,scipy/scipy,zerothi/scipy,gfyoung/scipy,bkendzior/scipy,Stefan-Endres/scipy,argriffing/scipy,Eric89GXL/scipy,anielsen001/scipy,lhilt/scipy,pbrod/scipy,ilayn/scipy,ilayn/scipy,matthewalbani/scipy,endolith/scipy,jamestwebber/scipy,person142/scipy,anntzer/scipy,haudren/scipy,matthewalbani/scipy,grlee77/scipy,aeklant/scipy,WarrenWeckesser/scipy,WarrenWeckesser/scipy,WarrenWeckesser/scipy,anielsen001/scipy,andyfaff/scipy,pyramania/scipy,tylerjereddy/scipy,matthew-brett/scipy,zerothi/scipy,Stefan-Endres/scipy,perimosocordiae/scipy,behzadnouri/scipy,matthew-brett/scipy,woodscn/scipy,anielsen001/scipy,perimosocordiae/scipy,pbrod/scipy,aeklant/scipy,Stefan-Endres/scipy,WarrenWeckesser/scipy,sriki18/scipy,person142/scipy,mdhaber/scipy,jjhelmus/scipy,andyfaff/scipy,scipy/scipy,lhilt/scipy,mikebenfield/scipy,arokem/scipy,gfyoung/scipy,tylerjereddy/scipy,befelix/scipy,jamestwebber/scipy,gdooper/scipy,apbard/scipy,pbrod/scipy,pbrod/scipy,endolith/scipy,argriffing/scipy,Newman101/scipy,haudren/scipy,befelix/scipy,zerothi/scipy,dominicelse/scipy,anntzer/scipy,woodscn/scipy,jakevdp/scipy,woodscn/scipy,aarchiba/scipy,apbard/scipy,vigna/scipy,andyfaff/scipy,grlee77/scipy,nonhermitian/scipy,jor-/scipy,e-q/scipy,kalvdans/scipy,nmayorov/scipy,mikebenfield/scipy,zerothi/scipy,Stefan-Endres/scipy,josephcslater/scipy,Eric89GXL/scipy,mdhaber/scipy,mikebenfield/scipy,nonhermitian/scipy,kleskjr/scipy,pizzathief/scipy,perimosocordiae/scipy,lhilt/scipy,gdooper/scipy,Eric89GXL/scipy,nmayorov/scipy,maniteja123/scipy,maniteja123/scipy,arokem/scipy,mikebenfield/scipy,nmayorov/scipy,pbrod/scipy,gfyoung/scipy,perimosocordiae/scipy,behzadnouri/scipy,pizzathief/scipy,Stefan-Endres/scipy,ilayn/scipy,surhudm/scipy,bkendzior/scipy,perimosocordiae/scipy,Newman101/scipy,zerothi/scipy,jakevdp/scipy,vigna/scipy,arokem/scipy,scipy/scipy,gfyoung/scipy,dominicelse/scipy,haudren/scipy,bkendzior/scipy,surhudm/scipy,aeklant/scipy,pizzathief/scipy,gdooper/scipy,pschella/scipy,rgommers/scipy,jamestwebber/scipy,anielsen001/scipy,argriffing/scipy,apbard/scipy,anntzer/scipy,aeklant/scipy,nmayorov/scipy,woodscn/scipy,nmayorov/scipy,kleskjr/scipy,behzadnouri/scipy,kalvdans/scipy,jakevdp/scipy,apbard/scipy,vigna/scipy,jjhelmus/scipy,befelix/scipy,behzadnouri/scipy,jjhelmus/scipy,jakevdp/scipy,gdooper/scipy,sriki18/scipy,gertingold/scipy,befelix/scipy,scipy/scipy,surhudm/scipy,kleskjr/scipy,andyfaff/scipy,kalvdans/scipy,zerothi/scipy,rgommers/scipy,rgommers/scipy,surhudm/scipy,kleskjr/scipy,woodscn/scipy,haudren/scipy,endolith/scipy,matthew-brett/scipy,anntzer/scipy,maniteja123/scipy,andyfaff/scipy,jamestwebber/scipy,endolith/scipy,apbard/scipy,Newman101/scipy,person142/scipy,rgommers/scipy,scipy/scipy,bkendzior/scipy,matthew-brett/scipy,pschella/scipy,anntzer/scipy,kleskjr/scipy,befelix/scipy,nonhermitian/scipy,matthewalbani/scipy,anntzer/scipy,WarrenWeckesser/scipy,argriffing/scipy,pizzathief/scipy,jor-/scipy,vigna/scipy,matthew-brett/scipy,pbrod/scipy,surhudm/scipy,grlee77/scipy,gfyoung/scipy,tylerjereddy/scipy,arokem/scipy,jakevdp/scipy,josephcslater/scipy,scipy/scipy,maniteja123/scipy,arokem/scipy,pyramania/scipy,haudren/scipy,gertingold/scipy,pschella/scipy,behzadnouri/scipy,ilayn/scipy,dominicelse/scipy,jor-/scipy,gertingold/scipy,jjhelmus/scipy,gertingold/scipy,gertingold/scipy,pschella/scipy,lhilt/scipy,mdhaber/scipy,maniteja123/scipy,Eric89GXL/scipy,bkendzior/scipy,endolith/scipy,grlee77/scipy,jamestwebber/scipy,mdhaber/scipy,anielsen001/scipy,mdhaber/scipy,sriki18/scipy,kalvdans/scipy