Port screen shaders from other projects

[barotto]

It has been brought to my attention that current CRT shader is not very fast on older hardware. Could be worth it to import shaders from other projects like DosBox Daum.

I don't think it's about computer specs. On DosBox SVN (Daum version) 99% of shaders work pretty fast on the same machine. (i.e. CRT-geom-curved.fx shader, which IMO is a very good replica of a 90's CRT monitor, runs very fast.) Originally posted by @Chris12121978 in https://github.com/barotto/IBMulator/issues/44#issuecomment-485453958