Debug verbosity inconsistency

[Neil Booth <neil at daikokuya dot demon dot co dot uk>]

In doing this hook stuff, I noticed that the old code in toplev.c
would do debug output for starting and ending sourcefiles regardless
of debug info level, *except* for dwarf, where it was required to be
verbose.

However, code within dwarfout.c itself would merrily call the same
routines without having done such a check.

I maintained this behaviour by making the dwarf hooks into a thin
wrapper that would do a verbosity check before calling the meaty bit.
However, I doubt this is the behaviour we really want.

So, which is correct:

1) We should do this stuff iff verbose like toplev.c did for dwarf
2) We should do this stuff regardless like toplev.c did for non-dwarf
3) The current situation is correct (very unlikely IMO).

If someone tells me, I'll fix it in my next patch.

Neil.