MAINT: linalg: tighten _decomp_update
MAINT: linalg: tighten _decomp_update

Removed unused code, added declarations and cdivision blocks to generate
~2k fewer lines of C.

ilayn/scipy,chatcannon/scipy,niknow/scipy,jamestwebber/scipy,jakevdp/scipy,tylerjereddy/scipy,lhilt/scipy,person142/scipy,mdhaber/scipy,anntzer/scipy,gfyoung/scipy,gdooper/scipy,haudren/scipy,surhudm/scipy,Shaswat27/scipy,matthew-brett/scipy,Shaswat27/scipy,jjhelmus/scipy,ilayn/scipy,nmayorov/scipy,andyfaff/scipy,befelix/scipy,apbard/scipy,tylerjereddy/scipy,kleskjr/scipy,perimosocordiae/scipy,Eric89GXL/scipy,nonhermitian/scipy,perimosocordiae/scipy,argriffing/scipy,zerothi/scipy,maniteja123/scipy,josephcslater/scipy,Gillu13/scipy,matthewalbani/scipy,kleskjr/scipy,matthew-brett/scipy,ilayn/scipy,woodscn/scipy,pyramania/scipy,anielsen001/scipy,niknow/scipy,pyramania/scipy,nonhermitian/scipy,niknow/scipy,Shaswat27/scipy,nmayorov/scipy,jor-/scipy,maniteja123/scipy,mdhaber/scipy,vigna/scipy,mikebenfield/scipy,Newman101/scipy,nmayorov/scipy,endolith/scipy,larsmans/scipy,aarchiba/scipy,jor-/scipy,aeklant/scipy,Gillu13/scipy,Stefan-Endres/scipy,chatcannon/scipy,Eric89GXL/scipy,grlee77/scipy,Eric89GXL/scipy,anntzer/scipy,Newman101/scipy,anntzer/scipy,person142/scipy,apbard/scipy,Newman101/scipy,Gillu13/scipy,haudren/scipy,chatcannon/scipy,gertingold/scipy,jakevdp/scipy,Newman101/scipy,kalvdans/scipy,arokem/scipy,woodscn/scipy,pbrod/scipy,surhudm/scipy,WarrenWeckesser/scipy,aarchiba/scipy,scipy/scipy,argriffing/scipy,larsmans/scipy,arokem/scipy,pbrod/scipy,Gillu13/scipy,Stefan-Endres/scipy,niknow/scipy,pizzathief/scipy,scipy/scipy,gfyoung/scipy,WarrenWeckesser/scipy,nonhermitian/scipy,nmayorov/scipy,pyramania/scipy,argriffing/scipy,josephcslater/scipy,pschella/scipy,mdhaber/scipy,pyramania/scipy,tylerjereddy/scipy,zerothi/scipy,woodscn/scipy,WarrenWeckesser/scipy,surhudm/scipy,e-q/scipy,befelix/scipy,Newman101/scipy,arokem/scipy,vigna/scipy,nmayorov/scipy,kalvdans/scipy,behzadnouri/scipy,bkendzior/scipy,matthew-brett/scipy,gertingold/scipy,dominicelse/scipy,andyfaff/scipy,perimosocordiae/scipy,Eric89GXL/scipy,chatcannon/scipy,bkendzior/scipy,gdooper/scipy,anntzer/scipy,aarchiba/scipy,gdooper/scipy,tylerjereddy/scipy,aeklant/scipy,lhilt/scipy,jor-/scipy,anielsen001/scipy,gertingold/scipy,larsmans/scipy,josephcslater/scipy,argriffing/scipy,jjhelmus/scipy,kalvdans/scipy,mdhaber/scipy,pizzathief/scipy,gertingold/scipy,argriffing/scipy,ilayn/scipy,kalvdans/scipy,behzadnouri/scipy,e-q/scipy,surhudm/scipy,pschella/scipy,perimosocordiae/scipy,vigna/scipy,perimosocordiae/scipy,jakevdp/scipy,aeklant/scipy,larsmans/scipy,vigna/scipy,zerothi/scipy,pizzathief/scipy,nonhermitian/scipy,dominicelse/scipy,haudren/scipy,anntzer/scipy,arokem/scipy,arokem/scipy,jjhelmus/scipy,jamestwebber/scipy,grlee77/scipy,aeklant/scipy,endolith/scipy,e-q/scipy,mikebenfield/scipy,zerothi/scipy,vigna/scipy,behzadnouri/scipy,Gillu13/scipy,matthewalbani/scipy,larsmans/scipy,gfyoung/scipy,grlee77/scipy,endolith/scipy,gdooper/scipy,bkendzior/scipy,apbard/scipy,sriki18/scipy,maniteja123/scipy,andyfaff/scipy,scipy/scipy,niknow/scipy,tylerjereddy/scipy,kleskjr/scipy,anntzer/scipy,rgommers/scipy,kleskjr/scipy,sriki18/scipy,jamestwebber/scipy,pyramania/scipy,scipy/scipy,surhudm/scipy,apbard/scipy,Gillu13/scipy,dominicelse/scipy,Stefan-Endres/scipy,pizzathief/scipy,dominicelse/scipy,grlee77/scipy,ilayn/scipy,Stefan-Endres/scipy,bkendzior/scipy,e-q/scipy,apbard/scipy,matthewalbani/scipy,surhudm/scipy,person142/scipy,kleskjr/scipy,Shaswat27/scipy,befelix/scipy,person142/scipy,chatcannon/scipy,zerothi/scipy,scipy/scipy,dominicelse/scipy,aeklant/scipy,josephcslater/scipy,jamestwebber/scipy,befelix/scipy,pschella/scipy,andyfaff/scipy,rgommers/scipy,jjhelmus/scipy,pbrod/scipy,WarrenWeckesser/scipy,gertingold/scipy,Stefan-Endres/scipy,pizzathief/scipy,anielsen001/scipy,WarrenWeckesser/scipy,matthewalbani/scipy,endolith/scipy,rgommers/scipy,haudren/scipy,sriki18/scipy,jor-/scipy,gfyoung/scipy,maniteja123/scipy,rgommers/scipy,pbrod/scipy,mikebenfield/scipy,matthew-brett/scipy,Newman101/scipy,chatcannon/scipy,WarrenWeckesser/scipy,maniteja123/scipy,Eric89GXL/scipy,kleskjr/scipy,lhilt/scipy,mdhaber/scipy,bkendzior/scipy,nonhermitian/scipy,anielsen001/scipy,maniteja123/scipy,pbrod/scipy,endolith/scipy,argriffing/scipy,behzadnouri/scipy,anielsen001/scipy,lhilt/scipy,Stefan-Endres/scipy,Shaswat27/scipy,jjhelmus/scipy,scipy/scipy,person142/scipy,pschella/scipy,grlee77/scipy,kalvdans/scipy,matthew-brett/scipy,larsmans/scipy,woodscn/scipy,jakevdp/scipy,aarchiba/scipy,rgommers/scipy,matthewalbani/scipy,josephcslater/scipy,gdooper/scipy,jakevdp/scipy,niknow/scipy,endolith/scipy,behzadnouri/scipy,behzadnouri/scipy,perimosocordiae/scipy,gfyoung/scipy,e-q/scipy,sriki18/scipy,woodscn/scipy,anielsen001/scipy,sriki18/scipy,zerothi/scipy,haudren/scipy,andyfaff/scipy,jamestwebber/scipy,ilayn/scipy,woodscn/scipy,pbrod/scipy,jor-/scipy,haudren/scipy,aarchiba/scipy,lhilt/scipy,mikebenfield/scipy,sriki18/scipy,Eric89GXL/scipy,mikebenfield/scipy,andyfaff/scipy,befelix/scipy,mdhaber/scipy,Shaswat27/scipy,pschella/scipy