The ornamental design for a winevat, as shown and described.
FIG. 1 is a perspective view of the top and front wine vat showing my new design;
FIG. 2 is a bottom plan view thereof;
FIG. 3 is a top plan view thereof;
FIG. 4 is a front elevational view thereof, the rear elevational view being a mirror image thereof;
FIG. 5 is a left side elevational view thereof, the right side elevational view being a mirror image thereof; and,
FIG. 6 is a perspective view of the bottom and rear thereof.
The broken line showing of a circle in FIGS. 1 and 3 is included for the purpose of illustrating elements of the wine vat and forms no part of the claimed design.