define macro STATE_PROG_SYMS.
* sim-trace.c (trace_one_insn): Add variables abfd, symsize,
symbol_count, and asymbols. Call bfd_get_symtab_upper_bound
and bfd_canonicalize_symtab, to get symbol table on first use
and preserve it via STATE_PROG_SYMS for future calls to
bfd_find_nearest_line.