[m-dev.] for review: type specialisation round 2

[Simon Taylor]

> In my uncommitted changes for debugging, I have reorganized the tracing options
> along the lines of my proposal of a few weeks ago. In that proposal, this
> functionality is achieved by an option called -no-trace-optimized, which
> was the default; users can then specify --trace-optimized.
 
OK, I'll remove --disable-opt-for-trace from my changes.

Simon.