Set PTRACE_O_TRACEEXIT option and handle PTRACE_EVENT_EXIT events

Set PTRACE_O_TRACEEXIT option and handle PTRACE_EVENT_EXIT events

Do not assume that some syscalls do not generate syscall-exit-stops.
When syscalls fail for any reason they may generate syscall-exit-stops.

The solution is to wait for an actual exit reported by PTRACE_EVENT_EXIT
and print the end of unfinished exiting syscall properly.

* exit.c: Remove.
* Makefile.am (strace_SOURCES): Remove exit.c.
* linux/dummy.h (sys_exit): Alias to printargs_d.
* strace.c (ptrace_setoptions): Add PTRACE_O_TRACEEXIT bit.
(print_event_exit): New function.
(trace): Use it in case of PTRACE_EVENT_EXIT.
* syscall.c (trace_syscall_entering): Remove special handling
of SEN_exit.