The ornamental design for a cupholder, as shown and described.
FIG. 1 is a perspective view of the cup holder of the invention showing it
being mounted on an upright post, the post being shown in phantom lines
and forming no part of the present invention;
FIG. 2 is a top view of the cup holder of the invention;
FIG. 3 is a left side view of the cup holder in FIG. 1, the right side view
being a mirror image thereof;
FIG. 4 is a front view of the cup holder of FIG. 3; and,
FIG. 5 is a bottom view of the cup holder of FIG. 2.