add builtin function atan2pi and ldexp
add builtin function atan2pi and ldexp

The two cases are are generated by utest_math_gen.py.

Signed-off-by: Zhu Bingbing <d56607f5afd810afefde79c21a45ae3748d7bc8d@intel.com>
Reviewed-by: Zhigang Gong <e04a7b9b70b1e4c6318cf117dcd1a9056e14b97a@linux.intel.com>

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