I've had some time to think about this a little bit more, and I'm not completely convinced that it would be a good idea to back port a new machine code generator to 7.8. After all, that seems like a pretty major change to insert into what should theoretically be a stable release.
Agreed.
Perhaps it makes more sense to release 7.8 as-is and then focus attention on doing a stable release of 7.9/7.10/8.0/whatever. How far from being stable is 7.9 at this point? I've dabbled with it, but haven't done much serious work with it yet.
The _Regexp.PCRE module will not compile if you have a recent (from this spring) libpcre unless you have a Pike 7.8 from today.