link_warning fix

[Bruno Haible]

Roland McGrath writes:
> > It is necessary in the first place because #APP is turned on through a
> > strange sectionname in
> > 
> >     static const char <variable> __attribute__ ((section ("<sectionname>")));
> > 
> > for which gcc does not emit #NO_APP automatically by itself.
> 
> That is clearly a GCC bug.

I don't agree. We put a strange string "foobar\n#APP\n\t#" into the
section name. It is unreasonable to except that gcc will scan user
given strings to see if they contain assembler directives.

Bruno