build system: tidying up CONFIG_xxx names (suggested by Rob)

diff --git a/miscutils/Config.in b/miscutils/Config.in
index f8b4575..60b87c1 100644
--- a/miscutils/Config.in
+++ b/miscutils/Config.in
@@ -107,7 +107,7 @@
 	      # Run daily cron jobs at 4:40 every day:
 	      40 4 * * * /etc/cron/daily > /dev/null 2>&1
 
-config DEBUG_CROND_OPTION
+config FEATURE_CROND_D
 	bool "Support option -d to redirect output to stderr"
 	depends on CROND
 	default n