Comment 1 for bug 1575120

I downloaded the source and made changes that appear to work for me (2016 branch):
in pano_modify.cpp:
add
#include <math.h>

and replace abs() with fabs()

Slightly off topic, I asked google how to submit a patch but couldn't find an easy answer within the first few minutes.
For future reference, Is there a short and easy way to generate a patch for this rather easy example?
Thanks