The ornamental design for a luminaire, as shown and described.
FIG. 1 is a perspective view of a luminaire showing my new design;
FIG. 2 is a top view thereof;
FIG. 3 is a bottom view thereof; and
FIG. 4 is a cross-sectional view of the luminaire showing my new design,
viewed along the line 4--4 of FIG. 2, with the outer strings of the
luminaire removed from ease of illustration.