Fix multiline def block for 'def self.foo' pattern
Revert "Revert "Run handlers in their own coroutines""

Take two. We could not do this last time due to mismatch between FFI and
Lua C API for callbacks. Now with ljglibs in place we're pure FFI: back
again.

Conflicts:
	lib/howl/bindings.moon
	spec/keyhandler_spec.moon
Document howl.ui.Cursor