add 64-bit version of "clz"
add 64-bit version of "clz"

this patch passes following piglit test cases:

 piglit/framework/../bin/cl-program-tester generated_tests/cl/builtin/int/builtin-ulong-clz-1.0.generated.cl
 piglit/framework/../bin/cl-program-tester generated_tests/cl/builtin/int/builtin-long-clz-1.0.generated.cl

Signed-off-by: Homer Hsing <f17cb7083eb6a94c3fb9d8f09ceefa518f721ab2@intel.com>
Reviewed-by: Zhigang Gong <e04a7b9b70b1e4c6318cf117dcd1a9056e14b97a@linux.intel.com>

zhenyw/beignet,freedesktop-unofficial-mirror/beignet,wdv4758h/beignet,zhenyw/beignet,ignatenkobrain/beignet,wdv4758h/beignet,wdv4758h/beignet,zhenyw/beignet,ignatenkobrain/beignet,freedesktop-unofficial-mirror/beignet,ignatenkobrain/beignet,freedesktop-unofficial-mirror/beignet,freedesktop-unofficial-mirror/beignet,wdv4758h/beignet,zhenyw/beignet,ignatenkobrain/beignet,wdv4758h/beignet,ignatenkobrain/beignet,zhenyw/beignet