More fixes for invalid memory accesses, uncovered by valgrind and binary fuzzers.

More fixes for invalid memory accesses, uncovered by valgrind and binary fuzzers.

	PR binutils/17512
	* coffcode.h (coff_slurp_line_table): Initialise the parts of the
	line number cache that would not be initialised by the copy from
	the new line number table.
	(coff_classify_symbol): Allow for _bfd_coff_internal_syment_name
	returning NULL.
	* coffgen.c (coff_get_normalized_symbols): Get the external
	symbols before allocating space for the internal symbols, in case
	the get fails.
	* elf.c (_bfd_elf_slurp_version_tables): Only allocate a verref
	array if one is needed.  Likewise with the verdef array.
	* peXXigen.c (_bfd_XXi_swap_sym_in): Replace abort()'s with error
	messages.
	(_bfd_XXi_swap_aux_in): Make sure that all fields of the aux
	structure are initialised.
	(pe_print_edata): Avoid reading off the end of the data buffer.