Add `sigset64_t` and accompanying functions.

This doesn't address `struct sigaction` and `sigaction`. That will
come later.

Bug: http://b/72493232
Test: ran tests
Change-Id: I4134346757ce3a4dac6feae413361cec16223386
diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index 5c9a284..5c63c0f 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -229,12 +229,12 @@
 # signals
 int     __sigaction:sigaction(int, const struct sigaction*, struct sigaction*)  arm,mips,x86
 int     __rt_sigaction:rt_sigaction(int, const struct sigaction*, struct sigaction*, size_t)  all
-int     __rt_sigpending:rt_sigpending(sigset_t*, size_t)  all
-int     __rt_sigprocmask:rt_sigprocmask(int, const sigset_t*, sigset_t*, size_t)  all
-int     __rt_sigsuspend:rt_sigsuspend(const sigset_t*, size_t)  all
-int     __rt_sigtimedwait:rt_sigtimedwait(const sigset_t*, siginfo_t*, const timespec*, size_t)  all
+int     __rt_sigpending:rt_sigpending(sigset64_t*, size_t)  all
+int     __rt_sigprocmask:rt_sigprocmask(int, const sigset64_t*, sigset64_t*, size_t)  all
+int     __rt_sigsuspend:rt_sigsuspend(const sigset64_t*, size_t)  all
+int     __rt_sigtimedwait:rt_sigtimedwait(const sigset64_t*, siginfo_t*, const timespec*, size_t)  all
 int     ___rt_sigqueueinfo:rt_sigqueueinfo(pid_t, int, siginfo_t*)  all
-int     __signalfd4:signalfd4(int, const sigset_t*, size_t, int)  all
+int     __signalfd4:signalfd4(int, const sigset64_t*, size_t, int)  all
 
 # sockets
 int           __socket:socket(int, int, int)              arm,arm64,mips,mips64,x86_64
@@ -305,7 +305,7 @@
 
 int epoll_create1(int)  all
 int epoll_ctl(int, int op, int, struct epoll_event*)  all
-int __epoll_pwait:epoll_pwait(int, struct epoll_event*, int, int, const sigset_t*, size_t)  all
+int __epoll_pwait:epoll_pwait(int, struct epoll_event*, int, int, const sigset64_t*, size_t)  all
 
 int eventfd:eventfd2(unsigned int, int)  all
 
@@ -317,7 +317,7 @@
 int inotify_rm_watch(int, unsigned int)  all
 
 int __pselect6:pselect6(int, fd_set*, fd_set*, fd_set*, timespec*, void*)  all
-int __ppoll:ppoll(pollfd*, unsigned int, timespec*, const sigset_t*, size_t)  all
+int __ppoll:ppoll(pollfd*, unsigned int, timespec*, const sigset64_t*, size_t)  all
 
 ssize_t process_vm_readv(pid_t, const struct iovec*, unsigned long, const struct iovec*, unsigned long, unsigned long)  all
 ssize_t process_vm_writev(pid_t, const struct iovec*, unsigned long, const struct iovec*, unsigned long, unsigned long)  all