[PATCH] compat_uptr_t and compat_ptr

[PATCH] compat_uptr_t and compat_ptr

This creates compat_uptr_t (to represent a user mode pointer passed to
the kernel other than as a syscall parameter) and compat_ptr() to
convert it to a kernel pointer.

This fixes a couple of bugs in s390x (where the conversion of pointers
actually does something).