- remove NaN check from JSImmediate::fromDouble for 0.5% SunSpider speedup

        It turns out that doing this check costs more than it saves.
        
        * kjs/JSImmediate.h:
        (KJS::JSImmediate::fromDouble):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@27416 268f45cc-cd09-0410-ab3c-d52691b4dbfc