Fix `namePosition` for 2.10.1 and 2.11.0

The Scala compiler translates lazy values earlier (in typer) from 2.10.1 onwards. This makes some heuristics fail.

We needed to fixes in `namePosition`:

* don't call `lazyAccessor` on a lazy accessor (you'd get `NoSymbol`). Make sure you only call it on a lazy field that backs up a lazy val
* identify `lazy val Pattern(lv) = ..` inside `DefDef`s now (prior to 2.10.1 the `DefDef` would be added several phases later).

This fixes the IDE build for 2.10.1 and (probably) 2.11.0