make IPC_INFO visible to ipc system utilities only

[Egor Duda]

Corinna Vinschen wrote:
>>Currently IPC_INFO is defined whenever we include sys/sem.h, but struct
>>seminfo, which is returned by semctl(IPC_INFO) is defined only for
>>_KERNEL applications. This inconsistency breaks, for instance,
>>libmudflap builds. I believe there's no point to have IPC_INFO in
>>non-_KERNEL application
> 
> 
>   as long as we can't get semctl(IPC_INFO) results right anyway.
>   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>   What is the author trying to tell me here?!?

I was unclear here, probably. I meant that "userspace application", i.e. 
application which includes sys/sem.h but don't define _KERNEL, may call 
semctl(IPC_INFO), but result of this call will have no meaning for 
application since it can't interpret it.

So by "we" in underscored sentence i meant "userspace", non-system ipc 
application.

egor