PE fake section for C_SECTION syms

It's an odd thing to have objdump -x show a different section table
to objdump -h, but that can happen if swapping in symbols leads to
creating sections.  Setting SEC_LINKER_CREATED stops the display of
these sections, so that you get shown what is in the object file.

	* peXXigen.c (_bfd_XXi_swap_sym_in): Set SEC_LINKER_CREATED on
	fake section created for C_SECTION syms.  Don't zero asection
	fields that are already zero.