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/libc.arm.map b/libc/libc.arm.map
index 1ed4ec6..c345ba6 100644
--- a/libc/libc.arm.map
+++ b/libc/libc.arm.map
@@ -1325,6 +1325,7 @@
     endhostent;
     endnetent;
     endprotoent;
+    epoll_pwait64;
     fexecve;
     fflush_unlocked;
     fgetc_unlocked;
@@ -1356,28 +1357,47 @@
     posix_spawnattr_getschedparam;
     posix_spawnattr_getschedpolicy;
     posix_spawnattr_getsigdefault;
+    posix_spawnattr_getsigdefault64;
     posix_spawnattr_getsigmask;
+    posix_spawnattr_getsigmask64;
     posix_spawnattr_init;
     posix_spawnattr_setflags;
     posix_spawnattr_setpgroup;
     posix_spawnattr_setschedparam;
     posix_spawnattr_setschedpolicy;
     posix_spawnattr_setsigdefault;
+    posix_spawnattr_setsigdefault64;
     posix_spawnattr_setsigmask;
+    posix_spawnattr_setsigmask64;
     posix_spawn_file_actions_addclose;
     posix_spawn_file_actions_adddup2;
     posix_spawn_file_actions_addopen;
     posix_spawn_file_actions_destroy;
     posix_spawn_file_actions_init;
     posix_spawnp;
+    ppoll64;
+    pselect64;
     pthread_attr_getinheritsched;
     pthread_attr_setinheritsched;
     pthread_mutexattr_getprotocol;
     pthread_mutexattr_setprotocol;
     pthread_setschedprio;
+    pthread_sigmask64;
     sethostent;
     setnetent;
     setprotoent;
+    sigaddset64;
+    sigdelset64;
+    sigemptyset64;
+    sigfillset64;
+    sigismember64;
+    signalfd64;
+    sigpending64;
+    sigprocmask64;
+    sigsuspend64;
+    sigtimedwait64;
+    sigwait64;
+    sigwaitinfo64;
     swab;
     syncfs;
 } LIBC_O;