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/getpeername.c

@@ -31,7 +31,7 @@
 int getpeername(int fd, void *out_addr, uint32_t *out_addrsize) {
   if (!IsWindows()) {
     return getpeername$sysv(fd, out_addr, out_addrsize);
-  } else if (isfdkind(fd, kFdSocket)) {
+  } else if (__isfdkind(fd, kFdSocket)) {
     return getpeername$nt(&g_fds.p[fd], out_addr, out_addrsize);
   } else {
     return ebadf();