*: 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/libbb/appletlib.c b/libbb/appletlib.c
index 80380ae..8f3729f 100644
--- a/libbb/appletlib.c
+++ b/libbb/appletlib.c
@@ -55,8 +55,8 @@
 #ifdef SINGLE_APPLET_MAIN
 #undef ENABLE_FEATURE_INDIVIDUAL
 #define ENABLE_FEATURE_INDIVIDUAL 1
-#undef USE_FEATURE_INDIVIDUAL
-#define USE_FEATURE_INDIVIDUAL(...) __VA_ARGS__
+#undef IF_FEATURE_INDIVIDUAL
+#define IF_FEATURE_INDIVIDUAL(...) __VA_ARGS__
 #endif
 
 
@@ -179,10 +179,10 @@
 
 
 void lbb_prepare(const char *applet
-		USE_FEATURE_INDIVIDUAL(, char **argv))
+		IF_FEATURE_INDIVIDUAL(, char **argv))
 				MAIN_EXTERNALLY_VISIBLE;
 void lbb_prepare(const char *applet
-		USE_FEATURE_INDIVIDUAL(, char **argv))
+		IF_FEATURE_INDIVIDUAL(, char **argv))
 {
 #ifdef __GLIBC__
 	(*(int **)&bb_errno) = __errno_location();
@@ -224,7 +224,7 @@
 /* If not built as a single-applet executable... */
 #if !defined(SINGLE_APPLET_MAIN)
 
-USE_FEATURE_SUID(static uid_t ruid;)  /* real uid */
+IF_FEATURE_SUID(static uid_t ruid;)  /* real uid */
 
 #if ENABLE_FEATURE_SUID_CONFIG
 
@@ -500,7 +500,7 @@
 #else
 static inline void parse_config_file(void)
 {
-	USE_FEATURE_SUID(ruid = getuid();)
+	IF_FEATURE_SUID(ruid = getuid();)
 }
 #endif /* FEATURE_SUID_CONFIG */
 
@@ -754,10 +754,10 @@
 #if defined(SINGLE_APPLET_MAIN)
 	/* Only one applet is selected by the user! */
 	/* applet_names in this case is just "applet\0\0" */
-	lbb_prepare(applet_names USE_FEATURE_INDIVIDUAL(, argv));
+	lbb_prepare(applet_names IF_FEATURE_INDIVIDUAL(, argv));
 	return SINGLE_APPLET_MAIN(argc, argv);
 #else
-	lbb_prepare("busybox" USE_FEATURE_INDIVIDUAL(, argv));
+	lbb_prepare("busybox" IF_FEATURE_INDIVIDUAL(, argv));
 
 #if !BB_MMU
 	/* NOMMU re-exec trick sets high-order bit in first byte of name */
diff --git a/libbb/lineedit.c b/libbb/lineedit.c
index 7bcdb95..e0ab732 100644
--- a/libbb/lineedit.c
+++ b/libbb/lineedit.c
@@ -62,10 +62,10 @@
 
 #define ENABLE_FEATURE_GETUSERNAME_AND_HOMEDIR \
 	(ENABLE_FEATURE_USERNAME_COMPLETION || ENABLE_FEATURE_EDITING_FANCY_PROMPT)
-#define USE_FEATURE_GETUSERNAME_AND_HOMEDIR(...)
+#define IF_FEATURE_GETUSERNAME_AND_HOMEDIR(...)
 #if ENABLE_FEATURE_GETUSERNAME_AND_HOMEDIR
-#undef USE_FEATURE_GETUSERNAME_AND_HOMEDIR
-#define USE_FEATURE_GETUSERNAME_AND_HOMEDIR(...) __VA_ARGS__
+#undef IF_FEATURE_GETUSERNAME_AND_HOMEDIR
+#define IF_FEATURE_GETUSERNAME_AND_HOMEDIR(...) __VA_ARGS__
 #endif
 
 enum {
@@ -152,8 +152,8 @@
 	(*(struct lineedit_statics**)&lineedit_ptr_to_statics) = xzalloc(sizeof(S)); \
 	barrier(); \
 	cmdedit_termw = 80; \
-	USE_FEATURE_EDITING_FANCY_PROMPT(num_ok_lines = 1;) \
-	USE_FEATURE_GETUSERNAME_AND_HOMEDIR(home_pwd_buf = (char*)null_str;) \
+	IF_FEATURE_EDITING_FANCY_PROMPT(num_ok_lines = 1;) \
+	IF_FEATURE_GETUSERNAME_AND_HOMEDIR(home_pwd_buf = (char*)null_str;) \
 } while (0)
 static void deinit_S(void)
 {
@@ -1160,7 +1160,7 @@
 	if ((state->flags & SAVE_HISTORY) && state->hist_file)
 		save_history(str);
 #endif
-	USE_FEATURE_EDITING_FANCY_PROMPT(num_ok_lines++;)
+	IF_FEATURE_EDITING_FANCY_PROMPT(num_ok_lines++;)
 }
 
 #else /* MAX_HISTORY == 0 */
@@ -1442,7 +1442,7 @@
 
 /* leave out the "vi-mode"-only case labels if vi editing isn't
  * configured. */
-#define vi_case(caselabel) USE_FEATURE_EDITING(case caselabel)
+#define vi_case(caselabel) IF_FEATURE_EDITING(case caselabel)
 
 /* convert uppercase ascii to equivalent control char, for readability */
 #undef CTRL
diff --git a/libbb/mtab_file.c b/libbb/mtab_file.c
index 030b148..c9d9a69 100644
--- a/libbb/mtab_file.c
+++ b/libbb/mtab_file.c
@@ -12,4 +12,4 @@
 /* Busybox mount uses either /proc/mounts or /etc/mtab to
  * get the list of currently mounted filesystems */
 const char bb_path_mtab_file[] ALIGN1 =
-USE_FEATURE_MTAB_SUPPORT("/etc/mtab")SKIP_FEATURE_MTAB_SUPPORT("/proc/mounts");
+IF_FEATURE_MTAB_SUPPORT("/etc/mtab")IF_NOT_FEATURE_MTAB_SUPPORT("/proc/mounts");
diff --git a/libbb/procps.c b/libbb/procps.c
index c5e40bf..445e709 100644
--- a/libbb/procps.c
+++ b/libbb/procps.c
@@ -111,7 +111,7 @@
 {
 	closedir(sp->dir);
 	free(sp->argv0);
-	USE_SELINUX(free(sp->context);)
+	IF_SELINUX(free(sp->context);)
 	free(sp);
 }
 
diff --git a/libbb/read.c b/libbb/read.c
index 37503e8..a0c0cc6 100644
--- a/libbb/read.c
+++ b/libbb/read.c
@@ -315,7 +315,7 @@
 	char *sfx;
 	int fd;
 #if BB_MMU
-	USE_DESKTOP(long long) int FAST_FUNC (*xformer)(int src_fd, int dst_fd);
+	IF_DESKTOP(long long) int FAST_FUNC (*xformer)(int src_fd, int dst_fd);
 	enum { xformer_prog = 0 };
 #else
 	enum { xformer = 0 };
@@ -352,7 +352,7 @@
 				 || magic[0] != 'B' || magic[1] != 'Z'
 				) {
 					bb_error_msg_and_die("no gzip"
-						USE_FEATURE_SEAMLESS_BZ2("/bzip2")
+						IF_FEATURE_SEAMLESS_BZ2("/bzip2")
 						" magic");
 				}
 #if BB_MMU
diff --git a/libbb/xconnect.c b/libbb/xconnect.c
index f5d7983..1b4f4f7 100644
--- a/libbb/xconnect.c
+++ b/libbb/xconnect.c
@@ -151,7 +151,7 @@
  * port: if neither of above specifies port # */
 static len_and_sockaddr* str2sockaddr(
 		const char *host, int port,
-USE_FEATURE_IPV6(sa_family_t af,)
+IF_FEATURE_IPV6(sa_family_t af,)
 		int ai_flags)
 {
 	int rc;
@@ -269,9 +269,9 @@
 }
 
 #undef xsocket_type
-int FAST_FUNC xsocket_type(len_and_sockaddr **lsap, USE_FEATURE_IPV6(int family,) int sock_type)
+int FAST_FUNC xsocket_type(len_and_sockaddr **lsap, IF_FEATURE_IPV6(int family,) int sock_type)
 {
-	SKIP_FEATURE_IPV6(enum { family = AF_INET };)
+	IF_NOT_FEATURE_IPV6(enum { family = AF_INET };)
 	len_and_sockaddr *lsa;
 	int fd;
 	int len;
@@ -303,7 +303,7 @@
 
 int FAST_FUNC xsocket_stream(len_and_sockaddr **lsap)
 {
-	return xsocket_type(lsap, USE_FEATURE_IPV6(AF_UNSPEC,) SOCK_STREAM);
+	return xsocket_type(lsap, IF_FEATURE_IPV6(AF_UNSPEC,) SOCK_STREAM);
 }
 
 static int create_and_bind_or_die(const char *bindaddr, int port, int sock_type)
@@ -316,7 +316,7 @@
 		/* user specified bind addr dictates family */
 		fd = xsocket(lsa->u.sa.sa_family, sock_type, 0);
 	} else {
-		fd = xsocket_type(&lsa, USE_FEATURE_IPV6(AF_UNSPEC,) sock_type);
+		fd = xsocket_type(&lsa, IF_FEATURE_IPV6(AF_UNSPEC,) sock_type);
 		set_nport(lsa, htons(port));
 	}
 	setsockopt_reuseaddr(fd);
diff --git a/libbb/xfuncs_printf.c b/libbb/xfuncs_printf.c
index 6d0fa6e..5f56b36 100644
--- a/libbb/xfuncs_printf.c
+++ b/libbb/xfuncs_printf.c
@@ -420,7 +420,7 @@
 		const char *s = "INET";
 		if (domain == AF_PACKET) s = "PACKET";
 		if (domain == AF_NETLINK) s = "NETLINK";
-USE_FEATURE_IPV6(if (domain == AF_INET6) s = "INET6";)
+IF_FEATURE_IPV6(if (domain == AF_INET6) s = "INET6";)
 		bb_perror_msg_and_die("socket(AF_%s)", s);
 #else
 		bb_perror_msg_and_die("socket");