signal.c: use printaddr and umove_or_printaddr

signal.c: use printaddr and umove_or_printaddr

* signal.c (print_sigset_addr_len, decode_old_sigaction):
Use printaddr and umove_or_printaddr.
(sys_signal): Use printaddr.
(sys_sigprocmask, sys_sigpending, sys_rt_sigprocmask,
sys_rt_sigpending): Remove redundant checks for syserror.
(decode_new_sigaction): Use umove_or_printaddr.