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 front left perspective view thereof.
FIG. 3 is a left side view thereof.
FIG. 4 is a top view thereof; and,
FIG. 5 is a front left perspective view of the head lamp shown in FIGS. 1-4, with the head lamp mounted on a vehicle shown in de-emphasized and half-tone portions so as to illustrate environmental structures for the vehicle front. These portions form no part of the claimed invention. More particularly, in FIG. 5, 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. The broken lines which show portions of the head lamp in FIGS. 1-4 are included for the purpose of illustrating environment and form no part of the claimed design.