Code Style: Delete PRIVATE defines that are never used

Some ".c" files define *_PRIVATE macros, but those macros are
not used in any header file. Delete them.

These changes were created using the "make autostyle" from
32522, and then split into commits.

src/test/test_util_process.c

@@ -1,7 +1,6 @@
 /* Copyright (c) 2010-2019, The Tor Project, Inc. */
 /* See LICENSE for licensing information */
 
-#define UTIL_PROCESS_PRIVATE
 #include "orconfig.h"
 #include "core/or/or.h"