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/nt/struct/securityattributes.h

@@ -1,9 +1,8 @@
 #ifndef COSMOPOLITAN_LIBC_NT_STRUCT_SECURITYATTRIBUTES_H_
 #define COSMOPOLITAN_LIBC_NT_STRUCT_SECURITYATTRIBUTES_H_
+#include "libc/nt/struct/securitydescriptor.h"
 #if !(__ASSEMBLER__ + __LINKER__ + 0)
 
-struct NtSecurityDescriptor;
-
 struct NtSecurityAttributes {
   uint32_t nLength;
   struct NtSecurityDescriptor *lpSecurityDescriptor;