DOSBox-CRT

This is just a slightly modified version of the standard DOSBOX emulator. I have just hacked in my own shader which emulates some aspects of old CRT monitors, as I prefer to play emulated games with such a filter, and the built-in dosbox filters are not to my taste. I made this because I wanted it myself, but since I have it I thought I'd share it. There's probably lots of things which could be done better, but it's good enough for my needs right now, so leaving it like this for now.Not a major news item, obviously, and just one among countless contributions to open source that pass by unnoticed every day, but every now and then, it seems only prudent to highlight one.