Greatly improved "retro look" and accuracy

[sy2002]

As of the time of writing this, I (sy2002) have no idea about all the magic that is happening in various retro project to generate a greatly improved retro look and better accuracy like supporting the "smearing effects" that real CRT's had and that were pro-actively used by programmers back in the days. This issue is a research issue for M2M enhancements that eventually can support them and an obvious place where to test them would be the C64 for MEGA65 core. For the time being, this issue is used to collect info.

1. Tom Harte's CLK emulator offers some stunning features around this. Have a look at these screenshots:
   https://github.com/TomHarte/CLK/tree/3dc9b625a18833c0ac6b7ed9e2c9bd0142f70314#signal-processing

2. (Copied from our C64 core's ROADMAP.md) A MiSTer feature request from @paich64:
   Feature Request : Simulate the blending of colours when ALM and DCM are used in c64 games to produce non standard colours MiSTer-devel/C64_MiSTer#104

3. Here is even more info coming from @paich64 (Quoting him):

Such colour blending has been recently implemented for the C64 in the RGB2HDMI project.

RGB2HDMI is a modern solution to connect old computers to HDMI display.

For the commodore 64, 2 devices are needed :

1. the Copperdragon "VIC-II-dizer" FPGA board which produces so called "Lumacode"
   https://github.com/c0pperdragon/LumaCode/wiki/
   https://github.com/c0pperdragon/LumaCode/wiki/VIC-II-dizer-(for-the-C64-computer)

2. The Lumcode is then interpreted by RGB2HDMI
   https://github.com/hoglet67/RGBtoHDMI/wiki
   https://github.com/IanSB/RGBtoHDMI
   release 59 mentions the implementation of colours blending : https://github.com/IanSB/RGBtoHDMI/releases

3. In this issue, we have 2 pictures : On showing the display without colour blending and the second one showing the display with colour blending
   PAL Artifacts with c64videoenhancement board IanSB/RGBtoHDMI#20

4. This video describes the lumacode protocol is :
   https://www.youtube.com/watch?v=SBgo8oGFung