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/calls/getpriority-nt.c

@@ -46,6 +46,6 @@ textwindows int getpriority$nt(int ignored) {
     }
     abort();
   } else {
-    return winerr();
+    return __winerr();
   }
 }