Fix compilation on libevent2-only systems

Patch from rubiate; fixes bug 22219.  Remember, we don't support
libevent1 any more.

src/or/channelpadding.c

@@ -20,7 +20,7 @@
 #include "rephist.h"
 #include "router.h"
 #include "compat_time.h"
-#include <event.h>
+#include <event2/event.h>
 
 STATIC int channelpadding_get_netflow_inactive_timeout_ms(const channel_t *);
 STATIC int channelpadding_send_disable_command(channel_t *);

src/test/test_channelpadding.c

@@ -11,7 +11,7 @@
 #include "channelpadding.h"
 #include "compat_libevent.h"
 #include "config.h"
-#include <event.h>
+#include <event2/event.h>
 #include "compat_time.h"
 #include "main.h"
 #include "networkstatus.h"