[Dovecot] patch for mysterious maildir symlink error

[Mike Abbott]

This may resolve the mysterious "Maildir: Symlink destination doesn't exist" errors.

--- a/src/lib-storage/index/maildir/maildir-util.c
+++ b/src/lib-storage/index/maildir/maildir-util.c
@@ -91,7 +91,7 @@
 {
 	struct stat st;
 
-	if (lstat(path, &st) == 0 && (st.st_mode & S_IFLNK) != 0) {
+	if (lstat(path, &st) == 0 && (st.st_mode & S_IFMT) == S_IFLNK) {
 		/* most likely a symlink pointing to a nonexistent file */
 		mail_storage_set_critical(&mbox->storage->storage,
 			"Maildir: Symlink destination doesn't exist: %s", path);