Fix for OS X build issues

Fix for the issues raised in #409 to enable building on OS X and for the resulting builds to be redistributable.

This changes the CMakeLists.txt files to require OS X 10.7+ with x86_64 architecture (as is required to select libc++ which is required for WxWidgets). Also specifies that the libc++ standard library be used when building AnimView and MapEdit, which enable them to build.

Updated the Apple specific section of the cmake files to remove old code used to copy the frameworks in to the app bundle, which was not being selected/used. Added new code to automatically build redistributable builds which include the required libraries.