Fix var not found in __defineErrorSignalHandler__.

Was probably a merge mistake, causing "revisedStack" to be called from
outside the function that defines it locally. I moved those two lines
into the function, to the location where they were in the Qt4-version.
Fix very small memory leak.

Mainly annoying while using valgrind, but a bug nevertheless.
Apply some QWebSetting-settings already on init.

QWebSettings has some static settings. With this commit they are set
in Phantom::init instead of the WebPage constructor. Not only is this
cheaper in performance, some of those settings *must* be set only once
and will assert if set twice.
Don't pass the filename to webkit in loadModule.

This is because webkit aborts if the filename doesn't have a valid url
scheme, which it hasn't for the internal modules (for internal modules
the filename is like ":/modules/fs.js").
Print unhandled javascript exceptions.
Use standard ECMA syntax to define setters/getters

Use Object.defineProperty() instead of obj.__defineGetter__() and
obj.__defineSetter__(). Newer QtWebkit versions don't actually seem to
support the old syntax, at least for QObject-typed objects.