Bit exact gaussian blur for 16bit unsigned int
* bit-exact gaussian kernel for CV_16U
* SIMD optimization
* template GaussianBlurFixedPoint
* remove template specialization
* simd support for h3N121 uint16
* test for u16 gaussian blur
* remove unnecessary comments
* fix return type of raw()
* add typedef of native internal type in fixedpoint
* update return type of raw()