Webkit: "Search the web" does not respect user preferences

[nephele]

This is hrev55008 (hrev55009+3)
The webkit build is on commit 24f821fce0128e8fd28e97f064e891dfacc193a8

For reference this always uses google.com as a search engine, the default was changed in WebPositive to duckduckgo.com though, so this is a bit more noticeable now

[pulkomandy]

This is hardcoded in Source/WebKitLegacy/haiku/WebCoreSupport/ContextMenuClientHaiku.cpp

I see two options to change it:

• The browser could configure haikuwebkit to set a preferred search engine, that would be used here
• Or, this code could be changed to send a message to the browser, eventually triggering BrowserWindow::_VisitSearchEngine in WebPositive

I think the second solution makes more sense, ideally we should move as much as possible of the context menu handling inside WebPositive and not on WebKit side.