fix for compiling ios 2.4 opencv with xcode 5.1

I applied change from http://stackoverflow.com/questions/16983696/how-to-build-opencv-2-4-9-for-ios
( dirty fix ? ), and disabled an error ( maybe was ignored in previous xcode release )
There's another patch to apply to cmake scripts to allow framework compilation with xcode 5.1, cfr :
http://answers.opencv.org/question/30940/opencv-builds-on-lab-computer-but-not-laptop/?answer=31466#post-id-31466
The current cmake release, 2.8.12 , does not contain the fix , next release will be ok ( i think )