Minor fix to COFF .section change

[Mark E.]

Hi Nick,

> Looking at the source in obj-coff.c it seems that "d" type sections
> explicitly have SEC_DATA and SEC_LOAD set, whereas "w" sections do

> I assume that your proposed patch fixes this problem as well ?

Right. Changing the default will fix this, since "w" is given the default 
attribute.

> that creates a new target macro (eg TC_COFF_DEFAULT_SECTION_ATTRIBUTES) 

>  If you can also generate a
> paragraph to go into doc/internals.texi describing this new macro,

No problem. So I don't waste your time by guessing and guessing wrong, would 
please let me know where in internals.texi the paragraph should go?

Thanks,
Mark