* inferior.h (step_over_calls_kind): New enum to clarify values in

* inferior.h (step_over_calls_kind): New enum to clarify values in
step_over_calls.
* infcmd.c (step_over_calls): Change definition.
(step_1): Use new enum values in relation to step_over_calls.
(step_once): Ditto.
(until_next_command): Ditto.
* infrun.c (clear_proceed_status): Ditto.
(handle_inferior_event): Ditto.
* inferior.h (step_stop_if_no_debug): New variable.
* infrun.c (step_stop_if_no_debug): Declare.
(handle_inferior_event): Stop the step command if we entered a function without
line info.
(_initialize_infrun): New command 'set step-mode' to control the step command.
* infcmd.c (step_once): Switch to stepi mode if there is no line info
(and switching is enabled).