Resurrection of whiteknight's eval_pmc branch

[Gerhard R.]

> Is there an updated pull request for NQP?  The old request
> at https://github.com/perl6/nqp/pull/36 can no longer be
> automatically merged.

I've got my own branch in the NQP repository, see
https://github.com/perl6/nqp/compare/master...target-pbc

> In general, there seem to be a lot of references to ".main_sub"
> in the NQP patch that I'm thinking shouldn't be there, or should
> be called something else.

This should no longer be the case. I split the step 'evalpmc' into two
steps 'pbc' and 'init'. The former returns a PackfileView, the latter
runs the 'init' subs and return the 'main' sub. Whiteknight's original
patch stopped after 'pbc', which required invocations of main_sub() on
the caller side.

> Looking at Rakudo #102, I'm a little concerned that the patch seems
> to assume that $precomp.main_sub() is an equivalent replacement
> to the old $precomp[0]... if I understand the eval_pmc branch
> correctly, that's not necessarily the case.

I don't know - whiteknight is the person to ask as I started from his
original patch. All I can say is that the tests still pass...

-- gerdr