The ornamental design for a gasburner, as shown and described.
FIG. 1 is a top view of a first embodiment of a gas burner according to the present design;
FIG. 2 is a bottom view of the gas burner of FIG. 1;
FIG. 3 is a front view of the gas burner of FIG. 1;
FIG. 4 is a back view of the gas burner of FIG. 1;
FIG. 5 is a right side view of the gas burner of FIG. 1;
FIG. 6 is a left side view of the gas burner of FIG. 1;
FIG. 7 is a perspective view of the gas burner of FIG. 1; and,
FIG. 8 is a perspective view of a second embodiment of a gas burner according to the present design wherein the top, bottom, front, back, right and left side views thereof are mirror images of the corresponding views of the first embodiment shown in FIGS. 1-7.