BUG: integrate: fix refcounting bug in quad()
BUG: integrate: fix refcounting bug in quad()

Decref'ing was completely forgotten in the callback, add it back.

vigna/scipy,gertingold/scipy,befelix/scipy,befelix/scipy,Stefan-Endres/scipy,ilayn/scipy,anntzer/scipy,scipy/scipy,endolith/scipy,pizzathief/scipy,ilayn/scipy,matthew-brett/scipy,andyfaff/scipy,person142/scipy,perimosocordiae/scipy,perimosocordiae/scipy,e-q/scipy,rgommers/scipy,gertingold/scipy,pbrod/scipy,vigna/scipy,person142/scipy,Stefan-Endres/scipy,perimosocordiae/scipy,jjhelmus/scipy,scipy/scipy,person142/scipy,jakevdp/scipy,jjhelmus/scipy,apbard/scipy,grlee77/scipy,jor-/scipy,Eric89GXL/scipy,aarchiba/scipy,Stefan-Endres/scipy,aeklant/scipy,mdhaber/scipy,anntzer/scipy,lhilt/scipy,jor-/scipy,WarrenWeckesser/scipy,jjhelmus/scipy,zerothi/scipy,aarchiba/scipy,WarrenWeckesser/scipy,matthew-brett/scipy,Eric89GXL/scipy,arokem/scipy,andyfaff/scipy,zerothi/scipy,andyfaff/scipy,andyfaff/scipy,gfyoung/scipy,endolith/scipy,Stefan-Endres/scipy,scipy/scipy,mdhaber/scipy,josephcslater/scipy,gfyoung/scipy,pizzathief/scipy,Eric89GXL/scipy,befelix/scipy,zerothi/scipy,befelix/scipy,pbrod/scipy,aeklant/scipy,jor-/scipy,grlee77/scipy,e-q/scipy,scipy/scipy,nmayorov/scipy,vigna/scipy,lhilt/scipy,endolith/scipy,josephcslater/scipy,WarrenWeckesser/scipy,perimosocordiae/scipy,lhilt/scipy,apbard/scipy,apbard/scipy,Stefan-Endres/scipy,jamestwebber/scipy,jamestwebber/scipy,jakevdp/scipy,jor-/scipy,rgommers/scipy,scipy/scipy,Eric89GXL/scipy,vigna/scipy,WarrenWeckesser/scipy,endolith/scipy,ilayn/scipy,anntzer/scipy,aarchiba/scipy,ilayn/scipy,endolith/scipy,Stefan-Endres/scipy,pbrod/scipy,e-q/scipy,person142/scipy,nmayorov/scipy,nmayorov/scipy,josephcslater/scipy,arokem/scipy,scipy/scipy,perimosocordiae/scipy,jamestwebber/scipy,WarrenWeckesser/scipy,aarchiba/scipy,endolith/scipy,pizzathief/scipy,mdhaber/scipy,person142/scipy,jor-/scipy,matthew-brett/scipy,pbrod/scipy,gfyoung/scipy,befelix/scipy,matthew-brett/scipy,gertingold/scipy,pizzathief/scipy,aeklant/scipy,aeklant/scipy,jamestwebber/scipy,tylerjereddy/scipy,mdhaber/scipy,tylerjereddy/scipy,ilayn/scipy,pbrod/scipy,gfyoung/scipy,Eric89GXL/scipy,andyfaff/scipy,jakevdp/scipy,mdhaber/scipy,aarchiba/scipy,perimosocordiae/scipy,pbrod/scipy,rgommers/scipy,arokem/scipy,jjhelmus/scipy,Eric89GXL/scipy,jamestwebber/scipy,apbard/scipy,gertingold/scipy,e-q/scipy,jakevdp/scipy,anntzer/scipy,josephcslater/scipy,andyfaff/scipy,zerothi/scipy,nmayorov/scipy,grlee77/scipy,tylerjereddy/scipy,arokem/scipy,zerothi/scipy,jjhelmus/scipy,tylerjereddy/scipy,anntzer/scipy,grlee77/scipy,WarrenWeckesser/scipy,ilayn/scipy,zerothi/scipy,matthew-brett/scipy,apbard/scipy,gfyoung/scipy,jakevdp/scipy,vigna/scipy,grlee77/scipy,rgommers/scipy,gertingold/scipy,josephcslater/scipy,aeklant/scipy,tylerjereddy/scipy,arokem/scipy,lhilt/scipy,anntzer/scipy,e-q/scipy,lhilt/scipy,rgommers/scipy,pizzathief/scipy,nmayorov/scipy,mdhaber/scipy