yet more -v stuff

[Matthew Fluet]

> > I discovered yesterday an unfortunate side effect of using .S and -g: all
> > of the debugging information is relative to the pre-processed temporary
> > file that gcc creates, which is trashed at the end of the gcc invocation.
> > This makes debugging assembly files almost useless -- there isn't much to
> > step through in the .c file, and we can't really get through the assembly
> > files.
> > 
> > I see two sorts of solutions:
> ...
> 
> Two more solutions.
> 
> 1. Ignore it and don't pass the info to the gc.

That's a reasonable solution.  I guess it depends whether not the info
is really useful.  Once you recognize which GC_gc call is being invoked,
is it really reasonable to trace it back to some particular part of the
source program?  I suspect this was difficult with the C backend; it would
be more so with the x86 backend.