BUG: fix 'largest' option in lobpcg(), new _get_indx() helper
BUG: fix 'largest' option in lobpcg(), new _get_indx() helper

- fix proposed by Andrew Knyazev

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