libiproute: rename invarg(a,b) to invarg_1_to_2(a,b)

invarg(a,b) - "invalid argument", but how a and b enter the message?

invarg_1_to_2(a,b) is somewhat easier to read: "invalid argument 'a' to 'b'"

Audit of usage revealed a number of bad uses, with too long messages.

   text	   data	    bss	    dec	    hex	filename
 938848	    932	  17448	 957228	  e9b2c	busybox_old
 938788	    932	  17448	 957168	  e9af0	busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/slattach.c b/networking/slattach.c
index a500da6..14e0c19 100644
--- a/networking/slattach.c
+++ b/networking/slattach.c
@@ -27,7 +27,7 @@
 //usage:     "\n	-F	Disable RTS/CTS flow control"
 
 #include "libbb.h"
-#include "libiproute/utils.h" /* invarg() */
+#include "libiproute/utils.h" /* invarg_1_to_2() */
 
 struct globals {
 	int handle;
@@ -175,7 +175,7 @@
 	encap = index_in_strings(proto_names, proto);
 
 	if (encap < 0)
-		invarg(proto, "protocol");
+		invarg_1_to_2(proto, "protocol");
 	if (encap > 3)
 		encap = 8;
 
@@ -183,7 +183,7 @@
 	if (opt & OPT_s_baud) {
 		baud_code = tty_value_to_baud(xatoi(baud_str));
 		if (baud_code < 0)
-			invarg(baud_str, "baud rate");
+			invarg_1_to_2(baud_str, "baud rate");
 	}
 
 	/* Trap signals in order to restore tty states upon exit */