[conformal/btcdb] f373ba: Introduce new error to indicate that block is not ...

[Dale Rahn]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcdb
  Commit: f373ba3583122f07611fec4037caf9a2dc913876
      
https://github.com/conformal/btcdb/commit/f373ba3583122f07611fec4037caf9a2dc913876
  Author: Dale Rahn <dr...@dalerahn.com>
  Date:   2014-07-25 (Fri, 25 Jul 2014)

  Changed paths:
    M db.go
    M ldb/block.go

  Log Message:
  -----------
  Introduce new error to indicate that block is not found vs db error.

ok @davecgh