Patch from Colin Watson intended to give a clean Unix compile with GCC 4.

(Since we choose to compile with -Werror, this is particularly important.)

I haven't yet checked that the resulting source actually compiles cleanly with
GCC 4, hence not marking `gcc4-warnings' as fixed just yet.

[originally from svn r7041]

tree234.c

@@ -136,6 +136,7 @@ static void *add234_internal(tree234 * t, void *e, int index)
 	return orig_e;
     }
 
+    n = NULL; /* placate gcc; will always be set below since t->root != NULL */
     np = &t->root;
     while (*np) {
 	int childnum;