alloc2 used unnecessarily

alloc2 used unnecessarily

The bfd_alloc2 series of functions were invented to handle cases where
nmemb * size can overflow.  This patch changes some places where the
calculation can't overflow.

	* elf.c (bfd_section_from_shdr): Use bfd_zalloc rather than
	bfd_zalloc2.
	(assign_section_numbers): Likewise.
	(elf_map_symbols): Likewise, and bfd_alloc rather than bfd_alloc2.
	(_bfd_elf_map_sections_to_segments): Use bfd_malloc rather than
	bfd_malloc2, size_t amt, and unsigned tls_count.
	(rewrite_elf_program_header): Use bfd_malloc and size_t amt.
	* elflink.c (elf_create_symbuf): Use bfd_malloc.
	(elf_output_implib): Use bfd_alloc.