Suppress normal stop observer when it's problematic.

	Suppress normal stop observer when it's problematic.
        * inferior.h (suppress_normal_stop_observer): New.
        * infcall.c (call_function_by_hand): Disable stop events when
        doing function calls.
        * infmcd.c (suppress_normal_stop_observer): New.
        (finish_command_continuation): Call normal_stop observer
        explicitly.
        (finish_command): Disable stop events inside proceed.
        * infrun.c (normal_stop): Don't call normal stop observer if
        suppressed of if multi-step is in progress.