2014-07-16  Sharath Kamath  <s.kamath@samsung.com>

        Support KHR_fp16 extension in WebCL.

        Fixed #531

        Reviewed by Antonio.

        Add support to KHR_fp16 in WebCLExtensionsAccessor interface.

        Also check for isExtensionEnabled("KHR_fp16") when the program
        source has a "#pragma OPENCL EXTENSION cl_khr_fp16 : enable".
        If not enabled throw a WEBCL_EXTENSION_NOT_ENABLED exception.

        * Modules/webcl/WebCL.idl:
        * Modules/webcl/WebCLDevice.cpp:
        (WebCore::WebCLDevice::getInfo):
        * Modules/webcl/WebCLExtensionsAccessor.cpp:
        (WebCore::WebCLExtensionsAccessor<T>::enableExtension):
        (WebCore::WebCLExtensionsAccessor<T>::getSupportedExtensions):
        * Modules/webcl/WebCLKernelArgInfo.h:
        (WebCore::WebCLKernelArgInfo::extractTypeEnum):
        * Modules/webcl/WebCLProgram.cpp:
        (WebCore::WebCLProgram::build):
        * platform/opencl/ComputeExtensionsCL.cpp:
        (WebCore::ComputeExtensions::supportsExtension):