Albin Bernhardsson

`etcpack.cxx` (possibly other files) extensively uses `static enum`. This is not valid C/C++ (and doesn't make any sense). `static` determines how storage should be allocated but an enum-declaration does not...

In the `FFX_VARIABLESHADING_ADDITIONALSHADINGRATES` version, the 1x2 shading rate is calculated using the 2x1 delta. This leads to 1x1 being used instead of 1x2.