With this change it is possible to send file descriptors to PID 1, via
sd_pid_notify_with_fds() which PID 1 will store individually for each
service, and pass via the usual fd passing logic on next invocation.
This is useful for enable daemon reload schemes where daemons serialize
their state to /run, push their fds into PID 1 and terminate, restoring
their state on next start from the data in /run and passed in from PID
1.
The fds are kept by PID 1 as long as no POLLHUP or POLLERR is seen on
them, and the service they belong to are either not dead or failed, or
have a job queued.
Emacs C indenting really gets confused by these lines if they carry no
trailing semicolon, hence let's make this nicer for good old emacs. The
other macros which define functions already do this too, so let's copy
the scheme here.
Also, let's use an uppercase name for the macro. So far our rough rule
was that macros that are totally not function-like (like this ones,
which define a function) are uppercase. (Well, admittedly it is a rough
rule only, for example function and variable decorators are all
lower-case SINCE THE CONSTANT YELLING IN THE SOURCES WOULD SUCK, and
also they at least got underscore prefixes.) Also, the macros that
define functions that we already have are all uppercase, so let's do the
same here...
