use native_exp function in opencl kernel for bilateral
use native_exp function in opencl kernel for bilateral

arrayfire/arrayfire,munnybearz/arrayfire,marbre/arrayfire,umar456/arrayfire,shehzan10/arrayfire,marbre/arrayfire,victorv/arrayfire,arrayfire/arrayfire,umar456/arrayfire,marbre/arrayfire,9prady9/arrayfire,umar456/arrayfire,9prady9/arrayfire,umar456/arrayfire,arrayfire/arrayfire,victorv/arrayfire,victorv/arrayfire,shehzan10/arrayfire,shehzan10/arrayfire,victorv/arrayfire,9prady9/arrayfire,munnybearz/arrayfire,marbre/arrayfire,9prady9/arrayfire,shehzan10/arrayfire,munnybearz/arrayfire,arrayfire/arrayfire