When copying pe format files, copy the dos_message array, rather than re-initiialisin...

When copying pe format files, copy the dos_message array, rather than re-initiialising it.

	* libcoff-in.h (struct pe_tdata): Add dos_message field.
	* libcoff.h: Regenerate.
	* peXXigen.c (_bfd_XXi_only_swap_filehdr_out): Copy the
	dos_message field rather than initialising it.
	(_bfd_XX_bfd_copy_private_bfd_data_common): Copy the dos_message
	field.
	* peicode.h (pe_mkobject): Initialise the dos_message field.
	(pe_mkobject_hook): Copy the dos_message field.
	(pe_bfd_object_p): Copy the dos_message field.