According to opencl 1.2 spec 6.1.5:
    For arguments to a __kernel function declared to be a pointer to a
    data type, the OpenCL compiler can assume that the pointee is always
    appropriately aligned as required by the data type. The behavior of
    an unaligned load or store is undefined, except for the
    vloadn, vload_halfn, vstoren, and vstore_halfn functions defined in
    section 6.12.7.

Original code read data of type T from address not aligned by multiple
of sizeof(T), so the result is incorrect. With this patch, the cases
./opencv_perf_imgproc
--gtest_filter=OCL_ImgSize_TmplSize_Method_MatType_MatchTemplate.MatchTemplate/*
could work well with beignet 0.9.3.
Signed-off-by: Chuanbo Weng <chuanbo.weng@intel.com>

The implicit narrowing in the initializer list throws a compiler error for some compilers with C++11 support turned on. The specific error message is: "error: narrowing conversion of 'PyInt_AsLong(((PyObject*)o))' from 'long int' to 'double' inside { }".

Tested on Clang 5.1.0 and Mac OS X 10.9.4.

- Accurate ASYC task handling for both GStreamer generations.
- Correct video duration request for videos.
- More accurate pipeline destruction.
- Correct color space conversion plugin for GStreamer 1.0.