kernel/hammer: Remove unused variables and add __debugvar.
kernel: Replace the remaining __amd64__ with __x86_64__ for consistency.
kernel/aac: sge64 is only used on x86_64.
kernel/linprocs: Remove some unused variables.
kernel/tcp_{input,output}: Remove some unused variables.
kernel/802_11: Remove unused variables.
kernel/netproto: Remove some unused variables.
kernel/nfs: Add a 'break' for readability and remove unneeded semicolon.
kernel: Remove some unused variables in RAID and disk drivers.
kernel/bus: Remove some unused variables and put others in #ifdef...
kernel/vfs: Remove some unused variables.
kernel/netinet: Remove some unused variables.
kernel/sound: Remove some unused variables.
kernel/net: Remove some unused variables.
kernel: Remove some more unused variables in the network drivers.
kernel: Remove some unused variables in the serial drivers.
kernel: Remove some unused variables in the rest of the kernel tree.