[Vimperator] what about this new feature?

[yichao.zhang]

Hi olivier,
Thanks to vimperator's good design, it's easy to add that feature.
in vimperator/src/chrome/content/vimperator/mappings.js:
the mapping "P" implemented by:
    addDefaultMap(new Map([vimperator.modes.NORMAL], ["P"],
        function()
        {
            vimperator.open(readFromClipboard(),
                /\bpaste\b/.test(vimperator.options["activate"]) ?
                vimperator.NEW_TAB : vimperator.NEW_BACKGROUND_TAB);
        },
        {}
    ));

readFromClipboard() is a function from mozilla/browser/base/content/browser.js
and browser.js also provides a function getBrowserSelection(aCharLen).
so I just added a mapping that replacing readFromClipboard() by
getBrowserSelection(150).

-Yichao