Properly handle real SIGTRAPs.

Properly handle real SIGTRAPs.

* defs.h (ptrace_setoptions): Variable renamed to ptrace_setoptions_followfork.
* process.c (internal_fork): Ditto.
* strace.c (ptrace_setoptions_for_all): New variable.
(SYSCALLTRAP): New variable.
(error_msg_and_die): New function.
(test_ptrace_setoptions_for_all): New function.
(main): Call test_ptrace_setoptions_for_all() at init.
(handle_ptrace_event): Handle PTRACE_EVENT_EXEC (by ignoring it).
(trace): Check events and set ptrace options without -f too.
Check WSTOPSIG(status) not for SIGTRAP, but for SYSCALLTRAP.