Fix comment for func_filter_filelist.

[Ralf Wildenhues]

Hi Bruno,

Dunno whether I sent this before or not, but I have this tiny patch
lying around against gnulib-tool.  OK to push?

Thanks,
Ralf

    * gnulib-tool (func_filter_filelist): Fix comment.

diff --git a/gnulib-tool b/gnulib-tool
index b50b08b..68531a5 100755
--- a/gnulib-tool
+++ b/gnulib-tool
@@ -1406,7 +1406,7 @@ func_get_filelist ()
 # Processing: removed_prefix and removed_suffix are removed from each element,
 # added_prefix and added_suffix are added to each element.
 # removed_prefix, removed_suffix should not contain the characters "$`\{}[]^|.
-# added_prefix, added_suffix should not contain the characters \|.
+# added_prefix, added_suffix should not contain the characters \|&.
 func_filter_filelist ()
 {
   if test "$2" != "$nl" \