Always use matched specpdl entry to record call arguments (Bug#18473).

Always use matched specpdl entry to record call arguments (Bug#18473).
* lisp.h (record_in_backtrace): Adjust prototype.
* eval.c (record_in_backtrace): Return current specpdl level.
(set_backtrace_args, set_backtrace_nargs): Merge.  Adjust all users.
(eval_sub, Ffuncall): Record call arguments in matched specpdl
entry and use that entry in call to backtrace_debug_on_exit.
(apply_lambda): Likewise.  Get current specpdl level as 3rd arg.
(do_debug_on_call): Get current specpdl level as 2nd arg.