*: mass renaming of USE_XXXX to IF_XXXX
and SKIP_XXXX to IF_NOT_XXXX - the second one was especially
badly named. It was not skipping anything!

diff --git a/modutils/insmod.c b/modutils/insmod.c
index 90ed87a..c4fb927 100644
--- a/modutils/insmod.c
+++ b/modutils/insmod.c
@@ -24,7 +24,7 @@
 	 * or in $MODPATH.
 	 */
 
-	USE_FEATURE_2_4_MODULES(
+	IF_FEATURE_2_4_MODULES(
 		getopt32(argv, INSMOD_OPTS INSMOD_ARGS);
 		argv += optind - 1;
 	);