Add CTL_PROC back

commit eab03ac7bd3e0da99eb9dc068772a85a5e3f3577 aka
"[PATCH] Get rid of /proc/sys/proc" was good commit except strace(1) compile breakage it introduced:

system.c:1581: error: 'CTL_PROC' undeclared here (not in a function)

So, add dummy enum back.

---

 include/linux/sysctl.h |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -62,7 +62,7 @@ enum
 	CTL_KERN=1,		/* General kernel info and control */
 	CTL_VM=2,		/* VM management */
 	CTL_NET=3,		/* Networking */
-	/* was CTL_PROC */
+	CTL_PROC=4,		/* removal breaks strace(1) compilation */
 	CTL_FS=5,		/* Filesystems */
 	CTL_DEBUG=6,		/* Debugging */
 	CTL_DEV=7,		/* Devices */