More fixes for memory access errors triggered by attemps to examine corrupted binaries.

More fixes for memory access errors triggered by attemps to examine corrupted binaries.

	PR binutils/17512
	* dwarf.c (display_block): Do nothing if the block starts after
	the end of the buffer.
	(read_and_display_attr_value): Add range checks.
	(struct Frame_Chunk): Make the ncols and ra fields unsigned.
	(frame_need_space): Test for an ncols of zero.
	(read_cie): Fail if the augmentation data extends off the end of
	the buffer.
	(display_debug_frames): Add checks for read_cie failing.  Add
	range checks.
	* coff-h8300.c (rtype2howto): Replace abort with returning a NULL
	value.
	* coff-h8500.c (rtype2howto): Likewise.
	* coff-tic30.c (rtype2howto): Likewise.
	* coff-z80.c (rtype2howto): Likewise.
	* coff-z8k.c (rtype2howto): Likewise.
	* coff-ia64.c (RTYPE2HOWTO): Always return a valid howto.
	* coff-m68k.c (m68k_rtype2howto): Return a NULL howto if none
	could be found.
	* coff-mcore.c (RTYPE2HOWTO): Add range checking.
	* coff-w65.c (rtype2howto): Likewise.
	* coff-we32k.c (RTYPE2HOWTO): Likewise.
	* pe-mips.c (RTYPE2HOWTO): Likewise.
	* coff-x86_64.c (coff_amd64_reloc): Likewise.  Replace abort with
	an error return.
	* coffcode.h (coff_slurp_reloc_table): Allow the rel parameter to
	be unused.
	* coffgen.c (make_a_section_from_file): Check the length of a
	section name before testing to see if it is a debug section name.
	(coff_object_p): Zero out any uninitialised bytes in the opt
	header.
	* ecoff.c (_bfd_ecoff_slurp_symbolic_info): Test for the raw
	source being empty when there are values to be processed.
	(_bfd_ecoff_slurp_symbol_table): Add range check.
	* mach-o.c (bfd_mach_o_canonicalize_one_reloc): Likewise.
	(bfd_mach_o_mangle_sections): Move test for too many sections to
	before the allocation of the section table.
	(bfd_mach_o_read_symtab_strtab): If the read fails, free the
	memory and nullify the symbol pointer.
	* reloc.c (bfd_generic_get_relocated_section_contents): Add
	handling of a bfd_reloc_notsupported return value.
	* versados.c (EDATA): Add range checking.
	(get_record): Likewise.
	(process_otr): Check for contents being available before updating
	them.
	(versados_canonicalize_reloc): Add range check.