2013-09-02  Sharath Kamath  <s.kamath@samsung.com>

        WebCL::createContext - deviceType property is not used.
        Issue #283

        Reviewed by Antonio.

        As per specification, when user sends a Type in property param of createContext()
        and sends no devices the type must be used to fetch devices.

        Also the devices sent must belong to same platform.

        if either them is not satisfied need to send a error to the user.

        conformance/functionalityTesting/createContext.html
        conformance/basicoperations/cl_webcl_createContext.html
        @ [https://github.com/SRA-SiliconValley/webkit-webcl-conformance]

        * Modules/webcl/WebCL.h:
        (WebCore::WebCL::createContextBase):
        * Modules/webcl/WebCLDevice.cpp:
        (WebCore::WebCLDevice::platform):
        * Modules/webcl/WebCLDevice.h: