Ensure data pointer kept within bounds

	* dwarf.c (process_extended_line_op): Don't bump data pointer past
	end when strnlen doesn't find string terminator.
	(decode_location_expression): Remove dead code.
	(skip_attr_bytes): Remove const from end param.  Ensure data
	pointer doesn't pass end.
	(get_type_signedness): Remove const from end param.
	(read_and_display_attr_value): Ensure data pointer doesn't pass end.
	(display_debug_lines_raw, display_debug_lines_decoded): Likewise.
	(display_debug_pubnames_worker): Likewise.
	(display_debug_pubnames_worker): Use SAFE_BYTE_GET_AND INC rather
	than blindly incrementing data pointer.
	(display_debug_addr, display_debug_str_offsets): Likewise.  Don't
	compare pointers, compare lengths.