sigaction.2: srcfix: Add FIXME

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man2/sigaction.2

@@ -374,6 +374,10 @@ and
 fill in
 .I si_addr
 with the address of the fault.
+.\" FIXME SIGTRAP also sets the following for ptrace_notify() ?
+.\"     info.si_code = exit_code;
+.\"     info.si_pid = task_pid_vnr(current);
+.\"     info.si_uid = current_uid();  /* Real UID */
 On some architectures,
 these signals also fill in the
 .I si_trapno