fix handling of self closing tags, like <hr/>

Use empty_element_tags in HTML::Parser, distinguish
close events by $text argument (empry - self closing,
not empty - real </tag>) as it's documented.

No tags autoclosing, so '<br>' results in '<br>'.

Space is added before '/>', so '<hr/>' result in '<hr />'.

Fixes tickets #19063 and #25477.
treat * attr rule in the same way as any other

this means it can be regexp
make it possible to process attributes with callabacks
fixup
Update authors/contributors/copyright.  Fix spelling.
v0.10

    - RT3008 Changed examples to be XSS free
    - RT19063, RT25477 fixed handling of self closing tags,
      for example '<hr />'
    - * attribute rule can be a regexp
    - callbacks in rules to check or adjust attributes with
      custom code (RT15747)