Comment bfd_get_section_limit_octets and bfd_get_section_alloc_size

	* bfd.c (bfd_get_section_limit_octets): Add comment.
	(bfd_get_section_alloc_size): Likewise.
	* libbfd.c (_bfd_generic_get_section_contents): Use
	bfd_get_section_limit_octets.
	* section.c (bfd_get_section_contents): Likewise.
	* bfd-in2.h: Regenerate.