Trivial toplev.c patch

[Stan Shebs]

Richard Kenner wrote:
> 
>     No, the right thing is to put ASM_FILE_START in the target structure;
>     anything else is just a temporary fix.
> 
> Please explain why you propose putting things that were perfectly clear as
> macros into some other mechanism.
> 
> I can understand using the target structure for places where things weren't
> already clean, but it seems a very heavy mechanism for something simple
> like this.

For consistency, which as you just pointed out is a desirable thing.
The mechanism isn't that heavyweight anyway - targetizing ASM_FILE_START
will result in a net reduction in the amount of GCC code, since many
of these have functions already, so you eliminate the macro and use
the function directly.

Stan