Return an std::string to avoid memory management headaches.
While doing that, convert time.c to C++ so that
format_datetime directly returns an std::string.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
This includes using the C++ version of membuffer. There appears
to not have been a leak, because the buffer is freed in
flush_buffer(), but usage was somewhat inconsistent and hard to
follow.
Also, convert some string handling to std::string to avoid free()
madness.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>