Fix issue with duplicate class inclusions.
Fix issue with duplicate class inclusions.

When trying to load a class that shared a prefix with an existing
class on case insensitive file systems duplicate class errors could
occur.  This would happen primarily with models and missing model classes.

Fixes #2223

tenkoma/cakephp,Phillaf/cakephp,tenkoma/cakephp,thinkingmedia/cakephp,dkarvounaris/cakephp,dakota/cakephp,petteyg/cakephp,dakota/cakephp,cakephp/cakephp,thinkingmedia/cakephp,ndm2/cakephp,berrygoudswaard/cakephp,justinyost/cakephp,CVO-Technologies/cakephp,burriko/cakephp,adopico/cakephp,CVO-Technologies/cakephp,khoimt/cakephp-study,tisu2tisu/cakephp,ndm2/cakephp,jerems02/cakephp,nrother/cakephp,khoimt/cakephp-study,jerems02/cakephp,jerems02/cakephp,Balachan27/cakephp,yinhe007/cakephp,cakephp/cakephp,elboletaire/cakephp,yinhe007/cakephp,davidyell/cakephp,timhoeppner/cakephp,akintoey/cakephp,burriko/cakephp,Phillaf/cakephp,pbaire/cakephp,yinhe007/cakephp,eryw/cakephp,et304383/passbolt_api,CVO-Technologies/cakephp,dkarvounaris/cakephp,akintoey/cakephp,erikfig/cakephp,et304383/passbolt_api,tenkoma/cakephp,petteyg/cakephp,timhoeppner/cakephp,pbaire/cakephp,elboletaire/cakephp,ADmad/cakephp,jjj117/cakephp,petteyg/cakephp,bravo-kernel/cakephp,timhoeppner/cakephp,adopico/cakephp,Balachan27/cakephp,eryw/cakephp,berrygoudswaard/cakephp,jeffblack360/cakephp,michaelze/cakephp,adopico/cakephp,nrother/cakephp,dakota/cakephp,jeffblack360/cakephp,web-player/cakephp,HavokInspiration/cakephp,elboletaire/cakephp,ADmad/cakephp,gmponos/cakephp,garethellis36/cakephp,ndm2/cakephp,tgr0ss/cakephp,justinyost/cakephp,davidyell/cakephp,tenkoma/cakephp,cakephp/cakephp,dkarvounaris/cakephp,jjj117/cakephp,justinyost/cakephp,gmponos/cakephp,cakephp/cakephp,tisu2tisu/cakephp,bravo-kernel/cakephp,ADmad/cakephp,eboominathan/cakephp,erikfig/cakephp,ADmad/cakephp,davidyell/cakephp,mvdriel/cakephp,burriko/cakephp,cakephp-fr/cakephp,CakeDC/cakephp,petteyg/cakephp,cakephp-fr/cakephp,tgr0ss/cakephp,CakeDC/cakephp,cakephp-fr/cakephp,web-player/cakephp,mvdriel/cakephp,khoimt/cakephp-study,kumamidori/cakephp,mvdriel/cakephp,gmponos/cakephp,tisu2tisu/cakephp,michaelze/cakephp,jeffblack360/cakephp,CakeDC/cakephp,CakeDC/cakephp,michaelze/cakephp,nrother/cakephp,Balachan27/cakephp,et304383/passbolt_api,et304383/passbolt_api,bravo-kernel/cakephp,ionas/cakephp,mvdriel/cakephp,garethellis36/cakephp,ionas/cakephp,eboominathan/cakephp,thinkingmedia/cakephp,kumamidori/cakephp,garethellis36/cakephp,HavokInspiration/cakephp,berrygoudswaard/cakephp,akintoey/cakephp,HavokInspiration/cakephp,erikfig/cakephp,Phillaf/cakephp,eryw/cakephp,tgr0ss/cakephp,jjj117/cakephp,garethellis36/cakephp,ndm2/cakephp,pbaire/cakephp,et304383/passbolt_api,web-player/cakephp,dakota/cakephp,eboominathan/cakephp,kumamidori/cakephp,ionas/cakephp