collection of small fixes from running runtime tests with -Xcomp

[Roland Westrelin]

> Currently, an L-type and the matching Q-type have the same memory 
> layout, so we could treat them as being the same. But by starting to 
> doing so we'll most likely encounter some difficult-to-trace errors. So 
> I'm more for bailing out compilations (or updating the type system to 
> consider Q-types as subclasses of java.lang.Object).

The problem in my case was that the root of the compilation is a lambda
form which takes and object argument but is passed a value type. There's
no way in that case to know at compile time that what is passed is a
value type so no way to bail out.

Roland.