https://bugs.webkit.org/show_bug.cgi?id=19180
        speed up SunSpider by optimizing immediate number cases

        Also fixed a JavaScriptCore regression seen on PowerPC - we didn't clip left shift
        parameter to 0...31.

        0.5% improvement on SunSpider overall, although a 8.5 regression on bitops-3bit-bits-in-byte.

        * VM/Machine.cpp:
        (KJS::Machine::privateExecute):
        Added fast paths for >>> and <<.

        * kjs/JSImmediate.h:
        (KJS::JSImmediate::toTruncatedUInt32): Added. Same as getTruncatedInt32, but casts the result
        to unsigned.



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@34265 268f45cc-cd09-0410-ab3c-d52691b4dbfc