(struct mach_msg_trap_args): New type.
(trampoline): Function removed.
(_hurd_setup_sighandler): Take struct hurd_sigstate * arg instead of FLAGS
and SIGALTSTACK args; take new flag arg RPC_WAIT; use struct
machine_thread_all_state * for STATE arg.
New declared labels `trampoline', `rpc_wait_trampoline' mark asm code at
end of function (after return).
Add another struct sigcontext * to STACKFRAME after the first one, for the
arg to __sigreturn.
If SS->context is set, fill registers in SCP from that instead of STATE,
and reset SS->INTR_PORT from it.
If RPC_WAIT is set, set up to use rpc_wait_trampoline and frob args to
mach_msg_trap syscall in progress so that it will retry the receive
operation (but not resend!).
{rpc_wait_trampoline, trampoline}: New trampoline code.
(_hurd_rcv_interrupted_p): New function.
