nixos/xserver: add option enableTearFree

        description = "Contents of the first Monitor section of the X server configuration file.";

      };

      enableTearFree = mkEnableOption "the TearFree option in the first Device section";

      extraConfig = mkOption {

        type = types.lines;

        default = "";

          Section "Device"

            Identifier "Device-${driver.name}[0]"

            Driver "${driver.driverName or driver.name}"

          ${indent (optionalString cfg.enableTearFree ''Option "TearFree" "true"'')}

          ${indent cfg.deviceSection}

          ${indent (driver.deviceSection or "")}

          ${indent xrandrDeviceSection}