Log Message:
Update to 1.18

Upstream changes:
- 1.18 H78M5qm1 Sat Jul 8 05:52:48:01 -0500 2017
      * fixed new() to check file or xml to detect standalone in
      declaration, from <HTTPS://RT.CPAN.Org/Ticket/Display.html?id=122389>
      (Thanks Alex!)

      * traced tidy() memory leak from
      <HTTPS://RT.CPAN.Org/Ticket/Display.html?id=120296> (Thanks Jozef!)
      which seems to come from every XPath->findnodes() call

      * aligned synopsis comments

      * updated write() to use output encoding UTF-8 since that's what
      almost all XML should rely on (with thanks to RJBS for teaching me
      much from his great talk at <HTTPS://YouTube.Com/watch?v=TmTeXcEixEg>)

      * collapsed trailing curly braces on code blocks

      * added croak for any failed file open attempt