Faster binornd using notmal approximation for large values

Behaves exactly like binornd, but uses a much faster normal approximation for large numbers,

This function takes the same input as the matlab built-in function binornd, and returns statistically (almost) identical output, potentially in much shorter time. For n,p values for which np,n(1-p)>5 a much fasternormal approximation is used with mean=np,var=np(1-p). For the rest, the regular binornd function is used.

This function can be faster by a factor of 5-10 than binornd for large numbers, but can be used the same way.