HTML corrector encodes (entifies) <!--break--> tag

The HTML corrector input filter mistakenly encodes (entifies) the less-than symbol in the "<!--break-->" tag. This results in the string <!--break--> being added to node output in some cases -- for example, in RSS feeds generated by taxonomy.module -- which displays the literal string "<!--break-->" at the summary split.

The patch adds a single line to _filter_htmlcorrector() that removes the string "<!--break-->" before entifying the less-than character.

+  // Remove the teaser separator before entifying angle brackets.
+  $text = str_replace('<!--break-->', '', $text);
+
   // Properly entify angles.
   $text = preg_replace('!<([^a-zA-Z/])!', '&lt;\1', $text);

This is a conservative patch intended to fix only the appearance of the "<!--break-->" tag. I propose expanding this chance to remove all HTML comments prior to coding the less-than character. To remove all HTML comments, the line $text = str_replace('<!--break-->', '', $text); above should be changed to:

$text = preg_replace('/<!--(.|\s)*?-->/', '', $text);

Reproducing the bug

1. Create a series of nodes using the "Full HTML" input filter.
2. Give these nodes unique summaries (teasers). That is, instead of "splitting" the node, give these nodes unique teasers that are not intended to be joined with the rest of the body. (This is achieved by unchecking "Show summary in full view" above the node's summary/body textareas.)
3. Tag each of these nodes with the same term.
4. View the RSS feed for that term (at example.com/taxonomy/term/TID/0/feed). You should see the literal text "<!--break-->" at the top of each item.

The "<!--break-->" tag is also visible on each node's Dev Load tab.