Use strdup(3) from string.h instead of own, fixes build with gcc 3.4

Add a few missing includes to silence warnings while i am here.

sysutils/xdu/files/patch-aa

@@ -1,6 +1,20 @@
---- xdu.c.orig	Mon Jun  6 04:29:23 1994
-+++ xdu.c	Fri Mar 16 07:20:49 2001
-@@ -235,6 +235,7 @@
+--- xdu.c.orig	Sun Jun  5 21:29:23 1994
++++ xdu.c	Sun Aug 15 19:31:01 2004
+@@ -20,9 +20,12 @@
+  * the party supplying this software to the X Consortium.
+  */
+ #include <stdio.h>
++#include <string.h>
++#include <stdlib.h>
++#include <unistd.h>
++#include <ctype.h>
+ #include "version.h"
+ 
+-extern char *malloc(), *calloc();
+ 
+ #define	MAXDEPTH	80	/* max elements in a path */
+ #define	MAXNAME		1024	/* max pathname element length */
+@@ -235,6 +238,7 @@
  	char	name[4096];
  	int	size;
  	FILE	*fp;
@@ -8,7 +22,7 @@
  
  	if (strcmp(filename, "-") == 0) {
  		fp = stdin;
-@@ -244,11 +245,21 @@
+@@ -244,11 +248,21 @@
  			exit(1);
  		}
  	}
@@ -31,7 +45,7 @@
  	fclose(fp);
  }
  
-@@ -269,7 +280,7 @@
+@@ -269,7 +283,7 @@
  	length = strlen(name);
  	if ((length > 0) && (name[length-1] == '/')) {
  		/* strip off trailing / (e.g. GNU du) */
@@ -40,7 +54,7 @@
  	}
  
  	arg = 0; indx = 0;
-@@ -289,8 +300,10 @@
+@@ -289,8 +303,10 @@
  		}
  		name++;
  	}
@@ -53,7 +67,7 @@
  	path[arg] = NULL;
  
  	addtree(&top,path,size);
-@@ -399,15 +412,15 @@
+@@ -399,15 +415,15 @@
  
  	/*printf("addtree(\"%s\",\"%s\",%d)\n", top->name, path[0], size);*/
  
@@ -75,3 +89,21 @@
  			/* recurse */
  			addtree(np,&path[1],size);
  			return;
+@@ -621,7 +637,7 @@
+ 	printf("%s %d (%.2f%%)\n", path, topp->size,
+ 		100.0*topp->size/rootp->size);
+ }
+-
++/*
+ char *
+ strdup(s)
+ char *s;
+@@ -635,7 +651,7 @@
+ 
+ 	return	cp;
+ }
+-
++*/
+ /**************** External Entry Points ****************/
+ 
+ int