mv, rm: adapt to new and improved gnulib interfaces

Use gnulib's new priv-set module and updated write-any-file.
With them, the remove-called can_write_any_file function no
longer tries to drop the unlink-directory privilege, so now
each caller of remove must do that separately, calling
priv_set_remove_linkdir.
* bootstrap.conf (gnulib_modules): Add priv-set.
* src/rm.c: Include "priv-set.h".
(main): Call priv_set_remove_linkdir.
* src/mv.c (main): Likewise.
* gnulib: Update submodule to latest.

bootstrap.conf

@@ -160,6 +160,7 @@ gnulib_modules="
   posix-shell
   posixtm
   posixver
+  priv-set
   progname
   propername
   putenv

gnulib

@@ -1 +1 @@
-Subproject commit 9ccd438ce337e6fb8c95d9261f1e06a3952261c2
+Subproject commit a771b77559753840d51609c779d526590e6a0144

src/mv.c

@@ -32,6 +32,7 @@
 #include "quote.h"
 #include "remove.h"
 #include "root-dev-ino.h"
+#include "priv-set.h"
 
 /* The official name of this program (e.g., no `g' prefix).  */
 #define PROGRAM_NAME "mv"
@@ -354,6 +355,9 @@ main (int argc, char **argv)
 
   cp_option_init (&x);
 
+  /* Try to disable the ability to unlink a directory.  */
+  priv_set_remove_linkdir ();
+
   /* FIXME: consider not calling getenv for SIMPLE_BACKUP_SUFFIX unless
      we'll actually use backup_suffix_string.  */
   backup_suffix_string = getenv ("SIMPLE_BACKUP_SUFFIX");

src/rm.c

@@ -55,6 +55,7 @@
 #include "remove.h"
 #include "root-dev-ino.h"
 #include "yesno.h"
+#include "priv-set.h"
 
 /* The official name of this program (e.g., no `g' prefix).  */
 #define PROGRAM_NAME "rm"
@@ -241,6 +242,9 @@ main (int argc, char **argv)
 
   rm_option_init (&x);
 
+  /* Try to disable the ability to unlink a directory.  */
+  priv_set_remove_linkdir ();
+
   while ((c = getopt_long (argc, argv, "dfirvIR", long_opts, NULL)) != -1)
     {
       switch (c)