Adding zoomswap patch (pertag compatible)

patch/zoomswap.c

@@ -0,0 +1,13 @@
+
+#if !PERTAG_PATCH
+static Client *prevzoom = NULL;
+#endif // PERTAG_PATCH
+
+Client *
+prevtiled(Client *c) {
+	Client *p;
+	if (!c || c == c->mon->clients)
+		return NULL;
+	for (p = c->mon->clients; p && p->next != c; p = p->next);
+	return p;
+}