Refactor Linux ipc_priv header

Refactor Linux ipc_priv header

Some architectures support the old-style IPC and require IPC_64 equal to
0x100 to be passed along SysV IPC syscalls, while new architectures should
default to new IPC version (without the flags being set).

This patch refactor current ipc_priv.h Linux headers in two directions:

- Remove cross platform references (for instance alpha including powerpc
  definition) and add required definition for each required port.  The
  idea is to avoid tie one architecture definition with another and make
  platform change independent.

- Move all common definitions (the ipc syscall commands) on a common
  header, ipc_ops.h.

	* sysdeps/unix/sysv/linux/aarch64/ipc_priv.h: New file.
	* sysdeps/unix/sysv/linux/alpha/ipc_priv.h: Avoid included other arch
	definition and define its own.
	* sysdeps/unix/sysv/linux/ipc_ops.h: New file.
	* sysdeps/unix/sysv/linux/x86_64/ipc_priv.h: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/ipc_priv.h: Likewise.
	* sysdeps/unix/sysv/linux/mips/ipc_priv.h: Remove file.
	* sysdeps/unix/sysv/linux/mips/mips64/ipc_priv.h: New file.
	* sysdeps/unix/sysv/linux/ipc_priv.h: Move ipc syscall operation
	definitions to common header.
	* sysdeps/unix/sysv/linux/powerpc/ipc_priv.h: Use common syscall
	operation from ipc_ops.h.