[[ Cocoa ]] Mainly clean up work to separate engine from platform.
[[ Cocoa ]] Fun with menus - something deep in Cocoa/Carbon doesn't currently like what we're doing...
[[ Cocoa ]] Sorted out MCPlatformMenuRef submenu reference count issue.
[[ Cocoa ]] Added getter for menuitem tag.
[[ Cocoa ]] Added API for MCPlatformCursorRef (not yet implemented).
[[ Cocoa ]] Initial cursor implementation (Mac).
[[ Cocoa ]] Added preliminary support for app menu.
[[ Cocoa ]] Finished initial cursor support.
[[ Cocoa ]] Work on window showing (dialogs, drawers, sheets).