Remove QuartzCore dependency on iOS

https://github.com/HaxeFoundation/hxcpp/blob/00985d5d768c1fac8a0f8b85d2bd52d4f2dea559/src/hx/Date.cpp#L35 adds a dependency on QuartzCore which make it more annoying to use haxe code in an ios Extension. However this is redundant anyway since `CACurrentMediaTime` is just a wrapper around `mach_absolute_time` which this code already supports for HX_MACOS. If I delete the IPHONE special case and change HX_MACOS case to HX_MACOS || IPHONE then everyting works