- Invoke htmlspecialchars() w/ fixed encoding

PHP defaults differ through the versions:
  . <= 5.3 uses iso-8859-1
  . 5.4, 5.5 uses utf-8
  . 5.6 uses "default_encoding"
Merge pull request #367 from kiesel/fix/htmlspecialchars

- Invoke htmlspecialchars() w/ fixed encoding