Fix debug build.
Update struct nchstats to 64 bit counters on all machines.
Remove the now-redundant struct nchstats_sysctl. Containerize
structure member names with a macro to eliminate cut-and-paste.
Update stats-keeping in sys/kern/vfs_cache.c to remove (most)
races while allowing consistent lockless sampling of the per-cpu
statistics without atomic operations.  Update comment describing
the locking protocol to include this.
Update stats-keeping in sys/kern/vfs_cache.c to remove (most)
races while allowing consistent lockless sampling of the per-cpu
statistics without atomic operations.  Update comment describing
the locking protocol to include this.

These files were fumble-fingered out of the last commit.