opaque types instead of union epoll_data

Hi All,

uapi structs epoll_data are more opaque than user space expects. kernel 
have defined as __u64 instead of the union epoll_data.
Because of this libc have redefined struct epoll_event with union data 
member.

https://android.googlesource.com/platform/bionic.git/+/master/libc/include/sys/epoll.h
typedef union epoll_data {
   void* ptr;
   int fd;
   uint32_t u32;
   uint64_t u64;
} epoll_data_t;
struct epoll_event {
   uint32_t events;
   epoll_data_t data;
}

Kernel UAPI header defined as "include/uapi/linux/eventpoll.h"
struct epoll_event {
         __u32 events;
         __u64 data;  =====>opaque type instead of union epoll_data
} EPOLL_PACKED;


Because of this we are landing into some issues as we copy kernel 
headers. Will it be going to be addressed?

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