Set sh_link for reloc sections created as normal sections

binutils-all/strip-13 and binutils-all/strip-14 tests create
SHT_REL/SHT_RELA sections by hand.  These don't have sh_link set to
the .symtab section as they should, leading to readelf warnings if you
happen to be looking at the object files.

	* elf.c (assign_section_numbers): Formatting.  Set sh_link for
	reloc sections created as normal sections in relocatable
	objects.