gas: re-arrange listing output for .irp and alike

gas: re-arrange listing output for .irp and alike

It is kind of odd to have the expansions of such constructs ahead of
their definition in listings with macro expansion enabled. Adjust this
by pulling ahead the output of the definition lines, taking care to
avoid producing a listing line for (non-existing) line 0 when the source
is stdin.

Note that with the code movement the conditional operator isn't
necessary anymore - list->line now match up.