Suggestion: Remove direct keyboard handling for active elements from NS Webkit Xwidgets

[Qiantan Hong]

Hi,

Currently, the GTK port seem to always let Emacs handle keyboard events, 
while NS port test if an INPUT/TEXTAREA element is active and let WKWebView
directly handle the keyboard events in those cases.

I think the GTK way is more flexible, as xwidget-webkit-edit-mode has shown one
can always pass through the event from Emacs side if desired. Shall we
remove those NS-specific code to make the behavior consistent across the two 
ports?

Best,
Qiantan