2014-06-23  Sharath Kamath  <s.kamath@samsung.com>

        Support KHR_fp64 extension in WebCL.

        Fixed #530

        Reviewed by Antonio.

        Add support to KHR_fp64 in WebCLExtensionsAccessor interface.
        For OpenCL1.2 implementation, "KHR_fp64" is enabled by default.

        Also check for isExtensionEnabled("KHR_fp64") when the program
        source has a "#pragma OPENCL EXTENSION cl_khr_fp64 : enable".
        If not enabled throw a WEBCL_EXTENSION_NOT_ENABLED exception.

        Adding support to Float64Array in setArg() API.

        * Modules/webcl/WebCLContext.h:
        * Modules/webcl/WebCLExtensionsAccessor.cpp:
        (WebCore::WebCLExtensionsAccessor<T>::enableExtension):
        (WebCore::WebCLExtensionsAccessor<T>::getSupportedExtensions):
        * Modules/webcl/WebCLProgram.cpp:
        (WebCore::WebCLProgram::isExtensionEnabled):
        (WebCore::WebCLProgram::build):
        * Modules/webcl/WebCLProgram.h:
        * platform/opencl/ComputeExtensionsCL.cpp:
        (WebCore::ComputeExtensions::supportsExtension):