kernel: Move sys/dev/acpica5 to sys/dev/acpica.

The 5 used to indicate that it was imported from FreeBSD 5 but that
doesn't matter anymore.

In-discussion-with: sephe
kernel: Remove unused variables in ACPI code (and add a __debugvar).
kernel: Remove some unused variables in bktr(4) and cxm(4).
Stop removing bsd.port.*.mk via 'make upgrade'.
kernel: Remove some unused variables in netgraph/netgraph7.