just starting filtering stuff. Doesn't work yet. Just getting files in place.

this two-dimensional bi-directional filtering scheme is going to replace the current averaging function I have (which works poorly and doesn't filter the way I want it to).
The averaging function kocks down noise to an average level. I want some legitimate first order signal filtering here.

new file:   SDL2_Testing/filters.c
new file:   SDL2_Testing/filters.h