Hampel filter in C++

Detect and replace outliers in a signal.

This function returns the Hampel filtered values of input data. This function is identical to
http://www.mathworks.se/matlabcentral/fileexchange/34795-outlier-detection-and-removal-hampel
, except that this implementation is in C++/mex and is significantly faster, especially for large datasets. One other difference is that the window width in this implementation is specified as a number of points, and not as an absolute width in for instance time.