The ornamental design for a headlamp, as shown and described.
FIG. 1 is a front view of a head lamp for a vehicle according to the present invention.
FIG. 2 is a rear view of the head lamp shown in FIG. 1.
FIG. 3 is a left side view thereof.
FIG. 4 is a right side view thereof.
FIG. 5 is a top view thereof.
FIG. 6 is a front three-quarter view thereof.
FIG. 7 is a rear three-quarter view thereof; and,
FIG. 8 is a front three-quarter view of the head lamp shown in FIG. 1, with the head lamp shown mounted on a vehicle that is depicted in de-emphasized and halftone portions so as to illustrate the environmental structure. These portions form no part of the claimed invention. More particularly, in FIG. 8, the head lamp of the present invention is shown within the broken lines, and any elements shown outside of the broken lines form no part of the claimed invention, but are instead included to show environmental aspects of the claimed invention.