struct mdisplaylist_s {
        unsigned int               gl_displaylist;       /*     0     4 */
        int                        rendermode;           /*     4     4 */
        float                      scrolloffset;         /*     8     4 */
        int                        renderDetailTexture;  /*    12     4 */

        /* size: 16, cachelines: 1, members: 4 */
        /* last cacheline: 16 bytes */
};

New field in msurface_t in HL25.

Compatibility with mods? Never heard of it!