lib: fix detection of ' as issue reference Commit 494c793cc160 changed HTML escaping to please HTML 4 email readers. The HTML entity ''' was replaced by '''. Unfortunately, the pound character '#' is often used to mark issue references, like 'bug #56'. While this depends on the issue patterns actually configured, this pattern is so common that we cannot expect users to set their issue_pat regular expressions such that '{' is not matched. Instead, keep the original ''' replacement at first in method html_escape, but introduce a final step that just replaces ''' with '''. The order of replacement in urlify_text then changes from: html_escape (to HTML4) urlify_issues to html_escape (to HTML5) urlify_issues make HTML5 more like HTML4 Test coverage show the problem case being solved.