simplexml callmap update (#723)
simplexml callmap update (#723)

* simplexml callmap update

fixes vimeo/psalm#722 and includes a number of manual updates to
simplexml function/method signatures (based on php.net docs)

* minor fixes

- s/qname/name/
- explicit void return type for `SimpleXMLElement::addAttribute()`

vimeo/psalm,vimeo/psalm