MAINT: squash some build warnings from `signal/_bspline_util.c.in`
MAINT: squash some build warnings from `signal/_bspline_util.c.in`

Stefan-Endres/scipy,Stefan-Endres/scipy,scipy/scipy,vigna/scipy,perimosocordiae/scipy,anntzer/scipy,ilayn/scipy,Stefan-Endres/scipy,rgommers/scipy,anntzer/scipy,scipy/scipy,endolith/scipy,endolith/scipy,mdhaber/scipy,WarrenWeckesser/scipy,WarrenWeckesser/scipy,vigna/scipy,vigna/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,vigna/scipy,scipy/scipy,endolith/scipy,perimosocordiae/scipy,rgommers/scipy,andyfaff/scipy,anntzer/scipy,perimosocordiae/scipy,andyfaff/scipy,ilayn/scipy,scipy/scipy,Stefan-Endres/scipy,mdhaber/scipy,anntzer/scipy,ilayn/scipy,WarrenWeckesser/scipy,rgommers/scipy,mdhaber/scipy,ilayn/scipy,mdhaber/scipy,perimosocordiae/scipy,WarrenWeckesser/scipy,rgommers/scipy,Stefan-Endres/scipy,endolith/scipy,vigna/scipy,anntzer/scipy,ilayn/scipy,scipy/scipy,scipy/scipy,WarrenWeckesser/scipy,endolith/scipy,endolith/scipy,Stefan-Endres/scipy,andyfaff/scipy,ilayn/scipy,andyfaff/scipy,rgommers/scipy,andyfaff/scipy,anntzer/scipy,andyfaff/scipy,mdhaber/scipy,perimosocordiae/scipy,mdhaber/scipy