Add experimental feature of opening a webbrowser, to show some of the

Add experimental feature of opening a webbrowser, to show some of the
webpages from http://www.ethereal.com. This functionality is copied from
the Gimp.
Win32 will use ShellExecute to use the system registered webbrowser.
On unix builds, currently the mozilla browser is hardcoded, we still need a
preference setting for this (I will add this later).

git-svn-id: http://anonsvn.wireshark.org/wireshark/trunk@11206 f5534014-38df-0310-8fa8-9805f1628bb7