OnKeyDown implemented for Form

[neurlang]

My app needs to detect both OnKeyUp() and OnKeyDown() on Form. Sadly. Only OnKeyUp() is provided. This implements OnKeyDown() in the existing Form path without affecting the lack of OnKeyDown() on Controls like combobox etc. This is because I don't need OnKeyDown() for form controls, just for the form.

Please check that the Accelerator support was not broken. If not, pls merge.