Module documentation for assorted modules, group 1

In aae034d1 I merged module documentation for these modules:

      buffers.c circuitstats.c command.c connection_edge.c control.c
      cpuworker.c crypto_curve25519.c crypto_curve25519.h
      crypto_ed25519.c crypto_format.c dircollate.c dirserv.c dns.c
      dns_structs.h fp_pair.c geoip.c hibernate.c keypin.c ntmain.c
      onion.c onion_fast.c onion_ntor.c onion_tap.c periodic.c
      protover.c protover.h reasons.c rephist.c replaycache.c
      routerlist.c routerparse.c routerset.c statefile.c status.c
      tor_main.c workqueue.c

Adding this ticket to track it.