mesa/st: add TGSI support for GL_FRAGMENT_SHADER_DERIVATIVE_HINT_ARB
TGSI has DDX and DDX_FINE, no DDX_COARSE. Currently the state tracker hardcodes ddx + coarse to DDX, and fine to DDX_FINE. It ignores the GL API hint for what to do with unadorned DDX instruction.
Now we could pipe all this into gallium with COARSE opcodes, and a new rasterizer state bit, but we could also not to do that.
This converts the DDX unadorned case to a DDX_UNK token, which is then lowered to either DDX or DDX_FINE before been given to the driver.
I wonder if we could just hacks the TGSI tokens in place, this overhead of a transform pass here likely sucks, but also TGSI is on the way out of here so maybe nobody cares