{patch bfd/ld/binutils]: Adjust calling convention of x64 windows to non-leading underscore

[Nick Clifton]

Hi Kai,

> This patch changes default for x64 windows targets to use
> non-underscored cdecl-symbols as described
> in vendor's calling-convention. This patch is the binutils part and a
> gcc patch will be posted soon for it, too.
> To allow the *old* behavior too, a bfd configure option
> '--enable-leading-mingw64-underscores' is added here.

Approved - please apply - but ...

... you need to document this new behaviour.  An entry in ld/NEWS to 
mention the new configure option and an update to the ld.texinfo file 
would be ideal.

Cheers
   Nick