Use semop syscall for Linux implementation

This patch add a direct call to semop syscall if it is supported by
kernel headers.

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

	* sysdeps/unix/sysv/linux/alpha/syscalls.list (semop): Remove.
	* sysdeps/unix/sysv/linux/arm/syscalls.list (semop): Likewise.
	* sysdeps/unix/sysv/linux/generic/syscalls.list (semop): Likewise.
	* sysdeps/unix/sysv/linux/hppa/syscalls.list (semop): Likewise.
	* sysdeps/unix/sysv/linux/ia64/syscalls.list (semop): Likewise.
	* sysdeps/unix/sysv/linux/microblaze/syscalls.list (semop): Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/syscalls.list (semop):
	Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/syscalls.list (semop):
	Likewise.
	* sysdeps/unix/sysv/linux/x86_64/syscalls.list (semop): Likewise.
	* sysdeps/unix/sysv/linux/semop.c (semop): Use semop syscall if it is
	defined.