Recover unescaped less-than character in HTML recovery parsing

As pointed by Christian Schoenebeck <schoenebeck@crudebyte.com>
on the list and based on some of his early patches, this preserve
content when unescaped opening angle brackets are not escaped in
textual content like:
  <p>  a < b </p>
  <p> a <0 </p>
  <p> a <=0 </p>

while still reporting the error.