(iOS) Gets things working again with iOS 7 SDK -

Starting from iOS 7, Apple "optimizes" sin and cos through
some function called __sincos_stret. This is however a new function
added by Apple in iOS 7/OSX 10.9 versions of libm. If you compile
a core with iOS 7/OSX 10.9 SDKs for an older platform, it will
crash on 'undefined symbol - __sincos_stret'. So I now set
minimum iPhone SDK version so that it doesn't do this "optimization"