A macro to determine if an SDL_Colorspace uses BT709 matrix coefficients.
Defined in <SDL3/SDL_pixels.h>
#define SDL_ISCOLORSPACE_MATRIX_BT709(cspace)        (SDL_COLORSPACEMATRIX(cspace) == SDL_MATRIX_COEFFICIENTS_BT709)| cspace | an SDL_Colorspace to check. | 
Returns true if BT709, false otherwise.
It is safe to call this macro from any thread.
This macro is available since SDL 3.2.0.