Define PS_USE_CLOBBER_ARGV on GNU/Hurd to (re-)enable process title changes.

Until d2ea2d3, the PS_USE_PS_STRINGS option
was used on the GNU Hurd. As this option got removed and PS_USE_CLOBBER_ARGV
appears to work fine nowadays on the Hurd, define this one to re-enable process
title changes on this platform.

Author: mbanck

src/backend/utils/misc/ps_status.c

@@ -52,7 +52,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 #define PS_USE_SETPROCTITLE_FAST
 #elif defined(HAVE_SETPROCTITLE)
 #define PS_USE_SETPROCTITLE
-#elif defined(__linux__) || defined(__sun) || defined(__darwin__)
+#elif defined(__linux__) || defined(__sun) || defined(__darwin__) || defined(__GNU__)
 #define PS_USE_CLOBBER_ARGV
 #elif defined(WIN32)
 #define PS_USE_WIN32
@@ -62,7 +62,7 @@ bool		update_process_title = DEFAULT_UPDATE_PROCESS_TITLE;
 
 
 /* Different systems want the buffer padded differently */
-#if defined(__linux__) || defined(__darwin__)
+#if defined(__linux__) || defined(__darwin__) || defined(__GNU__)
 #define PS_PADDING '\0'
 #else
 #define PS_PADDING ' '