Fix memory access violations triggered by running addr2line on fuzzed binaries.

Fix memory access violations triggered by running addr2line on fuzzed binaries.

	PR binutils/17512
	* dwarf.c (read_1_byte, read_1_signed_byte, read_2_bytes)
	(read_4_bytes, read_8_bytes, read_n_bytes, read_string)
	(read_indirect_string, read_alt_indirect_string)
	(read_alt_indirect_ref, read_address, read_abbrevs)
	(read_attribute_value, read_attribute, decode_line_info)
	(find_abstract_instance_name, read_rangelist)
	(scan_unit_for_symbols, parse_comp_unit)
	(_bfd_dwarf2_find_nearest_line): Harden DWARF reading code.  Pass
	end pointers to reading functions and check for offsets taking
	pointers out of range.  Replace calls to read_*_leb128 with calls
	to safe_read_leb128.

	(* elf64-ppc.c (opd_entry_value): Add a check for an overlarge
	offset.
	* syms.c (_bfd_stab_section_find_nearest_line): Add checks for
	computed file_name address being before the start of the string
	table.