sys/conf/files: Sort ACPI alphabetically.
kernel/libkern: Add strncat() to libkern.

In preparation for switching ACPI over to using various of our
kernel functions instead of its own versions.

Taken from libc.
kernel/acpica: Don't use ACPICA's own versions of various POSIX functions.

This removes the need to compile utclib.c into the kernel, so remove it
from the list.
kernel/acpica: Stop being prepared for using ACPICA's local cache.

We provide our own objcache(9) based one for some time now.