Disallow processing instructions in name tests

[GuntherRademacher]

A name test has been observed to return processing instructions in its result. This is reproducible by

declare function local:f($done, $todo) {
  if(empty($todo)) then $done else local:f(($done, head($todo)), tail($todo))
};
local:f((), (<e/>, <?pi?>))/self::*

It is caused by NameTest proceding to name matching as soon as kind == Kind.NODE, which also lets processing instructions slip through.

Fixed here by adding checks for Kind.ELEMENT and Kind.JNODE.