look into possible revert of @import

[incanus]

See background:

https://github.com/mapbox/mbxmapkit/commit/6c967bdd770413f4ad135706029e24d0582d2b9e#commitcomment-7643189

More details at:

http://stackoverflow.com/questions/20708262/using-import-in-objective-c-in-conjunction-with-cplusplus

Main problems are interaction with C++ code. For a while now Apple has been silently replacing #import <UIKit/UIKit.h> with the same effect as @import UIKit; but without compiler problems. Needs investigation as to whether this also auto-links imported frameworks without needing to manually edit the build phase, which was the main reasoning behind moving to this.