[RFA v2 00/24] More miscellaneous C++-ification

[Tom Tromey]

This is v2 of my miscellaneous C++-ification series.
v1 was here:

https://sourceware.org/ml/gdb-patches/2017-05/msg00073.html

... though I think for the reviews you will have to look in the June
archive.

I believe this series addresses all the review comments.  Some patches
have changed quite a bit; for example I took Pedro's suggestion to
change gdb_argv to a custom class (rather than a unique pointer).

I've added one more patch to the series, as now make_cleanup_freeargv
is no longer used, and so can be removed.

Regtested on the buildbot.

Tom