no_screen_flash updated to remove red flashes as well

[juef17]

It has been a request in the DWR discord server to have a way to remove the red flashes that happen upon death or walking onto swamp tiles and barrier tiles. This is done by changing all 17 bytes of the red-flashing code to all NOP bytes. Not very elegant, but it works very well. I'm not sure this is worth a flag in itself, given that those who dislike the spell flashing probably dislike the red flashes as well.

[Edit] Flag is implemented in this web app: here.