[Libguestfs] [PATCH nbdkit v2 0/4] Add -D nbdkit.environ=1, Windows fixes and quoting issues

This grew a bit from last time ... The basic change to allow dumping the environment is the same, except I enabled this for Windows (and checked that it does in fact work -- Windows has environment variables, who knew?) The second patch fixes a problem I noticed while testing the above on Windows. The third & fourth patches escape debug strings similarly to C strings, so for example if a debug string contains '\n' then it will be printed with ...\n... and not (as currently) break the debug message across multiple lines. Other non-printable characters are handled in the obvious way too. Rich.