Consolidate Linux msgctl implementation

Consolidate Linux msgctl implementation

This patch consolidates the msgctl Linux implementation in only
one default file, sysdeps/unix/sysv/linux/msgctl.c.  If tries to use
the direct syscall if it is supported, otherwise will use the old ipc
multiplex mechanism.

The patch also simplify header inclusion and reorganize internal
compat symbol to be built only if old ipc is defined.

Checked on x86_64, i686, powerpc64le, aarch64, and armhf.

	* sysdeps/unix/sysv/linux/alpha/Makefile (sysdeps_routines): Remove
	oldmsgctl.
	* sysdeps/unix/sysv/linux/alpha/msgctl.c: Remove file.
	* sysdeps/unix/sysv/linux/arm/msgctl.c: Likewise.
	* sysdeps/unix/sysv/linux/microblaze/msgctl.c: Likewise.
	* sysdeps/unix/sysv/linux/alpha/syscalls.list (oldmsgctl): Remove.
	* sysdeps/unix/sysv/linux/generic/syscalls.list (msgctl): Likewise.
	* sysdeps/unix/sysv/linux/hppa/syscalls.list (msgctl): Likewise.
	* sysdeps/unix/sysv/linux/ia64/syscalls.list (msgctl): Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/syscalls.list (msgctl):
	Likewise.
	* sysdeps/unix/sysv/linux/x86_64/syscalls.list (msgctl): Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/msgctl.c: Use default
	implementation.
	* sysdeps/unix/sysv/linux/msgctl.c (__new_msgctl): Use msgctl syscall
	if defined.