expression debugging

[Doug Evans]

When's the last time anyone did `set debug expression 1'?
[just curious how much bitrot I should expect]

Also, aren't dump_prefix_expression/dump_postfix_expression misnamed?
[should be the other way around]

parse.c:parse_exp_1:
  /* Convert expression from postfix form as generated by yacc
     parser, to a prefix form. */

  if (expressiondebug)
    dump_prefix_expression (expout, gdb_stdlog,
			    "before conversion to prefix form");

  prefixify_expression (expout);

  if (expressiondebug)
    dump_postfix_expression (expout, gdb_stdlog,
			     "after conversion to prefix form");