Blocks, functions, and methods now have the same code for handling
their bodies.
This means that single-line methods work like single-line functions:
they return the result of their expression.
They are now invoked like "new Foo".
Also, superclass constructors are now much less semantically
and syntactically weird. Since the instance is created before
any constructor is called, there's no point in time where the
instance isn't there.
This also fixes a bug where constructors weren't being bound
correctly, and eliminates some unneeded instructions when
compiling ifs.
I also tweaked the other method_call languages to match Wren's.
Since Wren needs to do a super call to get to the parent _count,
the other languages do now too.
This is nice too because it means we're benchmarking super
calls.
