[RFA v2 00/17] more C++

[Tom Tromey]

This is an updated version of my C++-ification series.  It has been
rebased on Pedro's unique_ptr patch, so it can't go in until that
does.

I think I've addressed all review comments.  (Though now that I am
writing this I remember I haven't yet dealt with the "override"
issue.)

I've added one more patch to remove some cleanups from captured_main.

Built and regtested on x86-64 Fedora 24.

Tom