A couple things that got tangled up in my tree, easier to check in both than
untangle them:

Rewrite u_signal_names() into get_signum() and get_signame(), plus trim the
signal list to that required by posix (they can specify the numbers for
the rest if they really need them).  (This is preparatory cleanup for adding
a timeout applet like Roberto Foglietta wants.)

Export the itoa (added due to Denis Vlasenko, although it's not quite his
preferred implementation) from xfuncs.c so it's actually used, and remove
several other redundant implementations of itoa and utoa() in the tree.

diff --git a/procps/fuser.c b/procps/fuser.c
index 1a4f612..2965fc3 100644
--- a/procps/fuser.c
+++ b/procps/fuser.c
@@ -9,18 +9,6 @@
  */
 
 #include "busybox.h"
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <string.h>
-#include <limits.h>
-#include <dirent.h>
-#include <signal.h>
-#include <sys/types.h>
-#include <sys/ioctl.h>
-#include <sys/stat.h>
-#include <sys/socket.h>
-#include <sys/sysmacros.h>
 
 #define FUSER_PROC_DIR "/proc"
 #define FUSER_MAX_LINE 255
@@ -335,7 +323,7 @@
 		optn = fuser_option(argv[i]);
 		if(optn) opt |= optn;
 		else if(argv[i][0] == '-') {
-			if(!(u_signal_names(argv[i]+1, &killsig, 0)))
+			if(0>(killsig = get_signum(argv[i]+1)))
 				killsig = SIGTERM;
 		}
 		else {
@@ -345,7 +333,6 @@
 	}
 	if(!fnic) return 1;
 
-	pids = xmalloc(sizeof(pid_list));
 	inodes = xmalloc(sizeof(inode_list));
 	for(i=0;i<fnic;i++) {
 		if(fuser_parse_net_arg(argv[fni[i]], &proto, &port)) {
@@ -354,14 +341,13 @@
 		else {
 			if(!fuser_file_to_dev_inode(
 				argv[fni[i]], &dev, &inode)) {
-				free(pids);
-				free(inodes);
-				bb_perror_msg_and_die(
-					"Could not open '%s'", argv[fni[i]]);
+				if (ENABLE_FEATURE_CLEAN_UP) free(inodes);
+				bb_perror_msg_and_die("Could not open '%s'", argv[fni[i]]);
 			}
 			fuser_add_inode(inodes, dev, inode);
 		}
 	}
+	pids = xmalloc(sizeof(pid_list));
 	success = fuser_scan_proc_pids(opt, inodes, pids);
 	/* if the first pid in the list is 0, none have been found */
 	if(pids->pid == 0) success = 0;