If it is called through libnghttp2 internally, name/value pairs are
all NULL-terminated.  But it is one of public API, and we cannot
expect that applications always make NULL-terminated string for
name/value pairs.

neverbleed is disabled by default.  To enable it, use
--with-neverbleed configure option.

Systemd assumes that service of type simple is stopped when the main
process exits. This causes systemd to kill all nghttpx processes when
doing a process upgrade (via USR2/QUIT signals). Change the service
type to forking which behaves correctly on upgrade.

This is meant to be used for ints, but unfortunately std::forward is
not constexpr in C++11.

Instead of assuming that upgrade is always successful, check if a new
process actually started. Do not kill old process if the new one
failed.