PR23994, libbfd integer overflow

PR23994, libbfd integer overflow

	PR 23994
	* aoutx.h: Include limits.h.
	(get_reloc_upper_bound): Detect long overflow and return a file
	too big error if it occurs.
	* elf.c: Include limits.h.
	(_bfd_elf_get_symtab_upper_bound): Detect long overflow and return
	a file too big error if it occurs.
	(_bfd_elf_get_dynamic_symtab_upper_bound): Likewise.
	(_bfd_elf_get_dynamic_reloc_upper_bound): Likewise.