[conformal/btcchain] 583406: Use block headers to generate node index.

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcchain
  Commit: 583406ee5115c3123405b1e68ea275039e6bf15f
      
https://github.com/conformal/btcchain/commit/583406ee5115c3123405b1e68ea275039e6bf15f
  Author: Dave Collins <da...@conformal.com>
  Date:   2014-01-19 (Sun, 19 Jan 2014)

  Changed paths:
    M accept.go
    M chain.go

  Log Message:
  -----------
  Use block headers to generate node index.

This commit changes the node index creation to use block headers instead
of full blocks.  This speeds up the initial node index generation since it
doesn't require loading a bunch of full blocks at startup.