rename seems missing from libc/libsys

[ccodere]

While trying to build using the new scripts, i discovered that the rename() function may not be present in libc.a for the linux68k platform. Maybe its something i missed on my side.

Default libc dumb implementation will be added in my branch.

[davidgiven]

Belatedly: rename() is a syscall, not a libc function, and so is provided by the plat's libsys. For the Linux plats, this is the shared libsys in plat/linux/libsys which is exceedingly basic and indeed doesn't have a rename().

Ideally all the syscalls should be automatically generated from a single description of what the system calls are but I haven't accumulated enough round tuits to do it yet.