Fix memory access problems discovered when running some binary tools on corrupt files.

Fix memory access problems discovered when running some binary tools on corrupt files.

	PR binutils/18758
	* elf.c (_bfd_elf_setup_sections): Add checks for corrupt section
	group information.
	* peicode.h (pe_ILF_make_a_section): Ensure alignment of the
	used_by_bfd pointer.
	(pe_ILF_build_a_bfd): Ensure alignment of vars.data pointer.