MFC r314866:

Reduce code duplication between MD Linux code by moving SYSV IPC 64-bit
related struct definitions out into the MI path.

Invert the native ipc structs to the Linux ipc structs convesion logic.
Since 64-bit variant of ipc structs has more precision convert native ipc
structs to the 64-bit Linux ipc structs and then truncate 64-bit values
into the non 64-bit if needed. Unlike Linux, return EOVERFLOW if the
values do not fit.

Fix SYSV IPC for 64-bit Linuxulator which never sets IPC_64 bit.