Write a bunch of module documentation.

This commit adds or improves the module-level documenation for:

  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

In particular, I've tried to explain (for each documented module)
what each module does, what's in it, what the big idea is, why it
belongs in Tor, and who calls it.  In a few cases, I've added TODO
notes about refactoring opportunities.

I've also renamed an argument, and fixed a few DOCDOC comments.

1 files changed, 8 insertions, 0 deletions

diff --git a/src/or/fp_pair.c b/src/or/fp_pair.c
index 53b311e580..eeeb0f1de3 100644
--- a/src/or/fp_pair.c
+++ b/src/or/fp_pair.c
@@ -7,6 +7,14 @@
  * \brief Manages data structures for associating pairs of fingerprints. Used
  * to handle combinations of identity/signing-key fingerprints for
  * authorities.
+ *
+ * This is a nice, simple, compact data structure module that handles a map
+ * from (signing key fingerprint, identity key fingerprint) to void *.  The
+ * fingerprints here are SHA1 digests of RSA keys.
+ *
+ * This structure is used in directory.c and in routerlist.c for handling
+ * handling authority certificates, since we never want more than a single
+ * certificate for any (ID key, signing key) pair.
  **/
 
 #include "or.h"