New regression, only linear as per recommendation of the Users' Guide

Exported functions and types prefixed with apt_
  Callback added for getsample, instead of calling named function.
  Allow library to be built without libpng or libsndfile.
Add support for building with MSVC on Windows.
Fix a few MSVC compiler warnings.
Fix nonlinear radiance correction for NOAA19.

The crop noise effect shifts the enetire image in memory, however when applying a map this shift did not get taken into account.

It didn't even work in the latest commit

Passes are flipped when northbound, not southbound

Why was this using a divide to calculate the difference?

Add linear equalise
Add image flip for southbound passes
Completly remove old falseclor in favour of a much simplier method

Change calibration to better suit constant gain
Add -Wextra to Makefile
Add link to model of the PLL
Max number of rows for the image is now increasible

Add a denoise filter
Fix temperature calibration
Tidy up some files
Improve MCIR

Add the ability to open a map overlay generated by wxmap (still unstable)
Remove the ability to turn off calibration
Add MCIR images
From now on large changes to neaten up the codebase will be taking place

Also made some floating-point math more explicit

Improved commenting in dsp.c
Updated copyright notices
Code tidy up in some parts

new dsp code
ngvi test