ia64 does not build

[Roland McGrath]

> ia64 does not build any more, due to missing __syscall_execve.  The
> problem is that linuxthreads/sysdeps/unix/sysv/linux/execve.c has higher
> priority than the execve entry in
> sysdeps/unix/sysv/linux/ia64/syscalls.list.  Any idea how to fix that
> other than marking the entry as EXTRA, or creating a syscalls.list in
> linuxthreads/sysdeps/unix/sysv/linux/ia64?

Ack.  The __syscall_* entries are already a kludge, and this only makes it
a little uglier.  I think marking s_execve et al as EXTRA will do.
Duplicating that line in a new
linuxthreads/sysdeps/unix/sysv/linux/ia64/syscalls.list might be more
completely proper, but several platforms would need a file added.

I don't know ia64 well, but unless it's somehow impossible for that
machine, just defining INLINE_SYSCALL is easier than continuing to maintain
the __syscall_* entry points.