Add epoll and do more release readiness changes

This change also pays off some of the remaining technical debt with
stdio, file descriptors, and memory managemnt polyfills.

libc/sock/getsockopt.c

@@ -39,7 +39,7 @@ int getsockopt(int fd, int level, int optname, void *out_opt_optval,
   if (optname == -1) return 0;                  /* our sysvconsts definition */
   if (!IsWindows()) {
     return getsockopt$sysv(fd, level, optname, out_opt_optval, out_optlen);
-  } else if (isfdkind(fd, kFdSocket)) {
+  } else if (__isfdkind(fd, kFdSocket)) {
     return getsockopt$nt(&g_fds.p[fd], level, optname, out_opt_optval,
                          out_optlen);
   } else {