file size check in _bfd_alloc_and_read

file size check in _bfd_alloc_and_read

	* coffgen.c (_bfd_coff_get_external_symbols): Remove file size check.
	* elf.c (bfd_elf_get_str_section): Likewise.
	(_bfd_elf_slurp_version_tables): Likewise.
	* libbfd-in.h (_bfd_constant_p): Define.
	(_bfd_alloc_and_read, _bfd_malloc_and_read): Check read size against
	file size before allocating memory.
	* libbfd.h: Regenerate.