Added more flexibility to webbrowser -> wget forwarding.

- Up to now the CTK program handler was necessary to start wget and forward the URL. Now alternatively the webbrowser uses the underlying OS to exec wget.

- Up to now windowed CTK was necessary to display the acknowledge dialog. Now alternatively the webbrowser displays the acknowledge text and buttons right in the webpage area.

- For now the targets 'win32' and 'c64' make use of the new capabilities.
Merge pull request #539 from oliverschmidt/master

Added more flexibility to webbrowser -> wget forwarding.