Get working support for PHP7 in core (all-in-one auto-generated branch)

AFAIK the only remaining core issues needed for PHP7 (MDL-50565) to work are:

1) Handful of syntax errors (improper break/continue, duplicate function args)
2) deprecated PHP4 style constructor usage in core and bundled libs
3) Testing, core handler, should gracefully deal with new Throwables
4) eval() may throw new ParseError and other Throwables

I've resolved these with some help from tests and a script to perform the bulk deprecated constructor updates (see: https://gist.github.com/tlevi/dd7930026cb5b0ef7b97) - this uses a proper php-parser, so it is a little more reliable than what I could cobble together with sed.