dpkg: On purge correctly remove a symlink pointing to a directory

The code was treating symlinks to directories as directories, but then
it was trying to rmdir(2) them, which failed. In such case just verify
it's a symlink and unlink(2) them instead.

debian/changelog

@@ -61,6 +61,8 @@ dpkg (1.16.1) UNRELEASED; urgency=low
   * On package removal, keep only directories actually containing conffiles,
     and not directories just matching the substring in the conffile or the
     directory itself. Thanks to Ondřej Surý <ondrej@debian.org>.
+  * On purge correctly remove symlinks acting as directories, when they are
+    not being used by any other package's files.
 
   [ Updated dpkg translations ]
   * German (Sven Joachim). Closes: #620312

src/remove.c

@@ -362,6 +362,15 @@ static void removal_bulk_remove_leftover_dirs(struct pkginfo *pkg) {
     }
     if (errno != ENOTDIR) ohshite(_("cannot remove `%.250s'"),fnvb.buf);
 
+    if (lstat(fnvb.buf, &stab) == 0 && S_ISLNK(stab.st_mode)) {
+      debug(dbg_eachfiledetail, "removal_bulk is a symlink to a directory");
+
+      if (unlink(fnvb.buf))
+        ohshite(_("cannot remove '%.250s'"), fnvb.buf);
+
+      continue;
+    }
+
     push_leftover(&leftover,namenode);
     continue;
   }