Make iOS build instructions more generic and applicable to all versions of Xcode;  modify iOS build procedure for Xcode 5.0 and later to fix a build issue with Xcode 5.1.


git-svn-id: svn://svn.code.sf.net/p/libjpeg-turbo/code/trunk@1216 632fc199-4ca6-4c93-a231-07263d6284db