Fix straggling MS_WINDOWS issues; add a changes file

There was one MS_WINDOWS that remained because it wasn't on a macro
line; a few remaining uses (and the definition!) in configure.in;
and a now-nonsensical stanza of eventdns_tor.h that previously
defined 'WIN32' if it didn't exist.

src/common/util.c

@@ -2972,7 +2972,7 @@ finish_daemon(const char *desired_cwd)
   close(daemon_filedes[1]);
 }
 #else
-/* defined(MS_WINDOWS) */
+/* defined(_WIN32) */
 void
 start_daemon(void)
 {