Fix cache clearing for ApcEngine.
Fix cache clearing for ApcEngine.

APCIterator is available only for APCu 5.0+.

tgr0ss/cakephp,berrygoudswaard/cakephp,ndm2/cakephp,dakota/cakephp,cakephp/cakephp,thinkingmedia/cakephp,jeffblack360/cakephp,ADmad/cakephp,dakota/cakephp,CVO-Technologies/cakephp,cakephp-fr/cakephp,ndm2/cakephp,dakota/cakephp,CakeDC/cakephp,garethellis36/cakephp,davidyell/cakephp,thinkingmedia/cakephp,jeffblack360/cakephp,ADmad/cakephp,mvdriel/cakephp,garethellis36/cakephp,mvdriel/cakephp,nrother/cakephp,cakephp-fr/cakephp,thinkingmedia/cakephp,cakephp/cakephp,tenkoma/cakephp,elboletaire/cakephp,cakephp-fr/cakephp,cakephp/cakephp,cakephp/cakephp,tenkoma/cakephp,petteyg/cakephp,CakeDC/cakephp,ADmad/cakephp,davidyell/cakephp,ndm2/cakephp,garethellis36/cakephp,petteyg/cakephp,CakeDC/cakephp,tgr0ss/cakephp,elboletaire/cakephp,CakeDC/cakephp,ionas/cakephp,berrygoudswaard/cakephp,jeffblack360/cakephp,garethellis36/cakephp,tenkoma/cakephp,HavokInspiration/cakephp,mvdriel/cakephp,nrother/cakephp,tenkoma/cakephp,ADmad/cakephp,petteyg/cakephp,petteyg/cakephp,tgr0ss/cakephp,ndm2/cakephp,berrygoudswaard/cakephp,nrother/cakephp,ionas/cakephp,ionas/cakephp,davidyell/cakephp,HavokInspiration/cakephp,elboletaire/cakephp,CVO-Technologies/cakephp,mvdriel/cakephp,CVO-Technologies/cakephp,dakota/cakephp,HavokInspiration/cakephp