Does the platform provide and support the library `unwind`?

Property definitions

	# Does the platform provide and support the library `unwind`?
	fun supports_libunwind: Bool do return true

src/platform/platform.nit:113,2--114,44

	redef fun supports_libunwind do return false

src/platform/android.nit:41,2--45

	redef fun supports_libunwind do return false

src/platform/emscripten.nit:35,2--45

	redef fun supports_libunwind do return false

src/platform/ios.nit:34,2--45