[phpbb] Adding Highlight options as IniSettings

This allows highlight_string to work properly after ini_set has been called on one of the highlight options (doesn't need ini file). http://www.php.net/manual/en/misc.configuration.php#ini.syntax-highlighting

fixes #1823
merged from #1826 

Not sure if my naming conventions are correct.
May fix a few of the tests in zend/bad; looking into it.