wuffs: update, add jpeg decoding, add simple tests

pkg/wuffs/src/error.zig

@@ -1,3 +1,13 @@
 const std = @import("std");
 
+const c = @import("c.zig").c;
+
 pub const Error = std.mem.Allocator.Error || error{WuffsError};
+
+pub fn check(log: anytype, status: *const c.struct_wuffs_base__status__struct) error{WuffsError}!void {
+    if (!c.wuffs_base__status__is_ok(status)) {
+        const e = c.wuffs_base__status__message(status);
+        log.warn("decode err={s}", .{e});
+        return error.WuffsError;
+    }
+}