Improve hashsocket() (for win32) to avoid collisions

Fixes: 91e3ead
Refs: https://gist.github.com/azat/8a0a94e4de2d95af8f729b709589ce12

evmap.c

@@ -95,7 +95,7 @@ hashsocket(struct event_map_entry *e)
 	 * matter.  Our hashtable implementation really likes low-order bits,
 	 * though, so let's do the rotate-and-add trick. */
 	unsigned h = (unsigned) e->fd;
-	h += (h >> 2) | (h << 30);
+	h = (h >> 2) | (h << 30);
 	return h;
 }