[conformal/btcwire] 7de20a: Add benchmark for writeBlockHeader.

[Dave Collins]

  Branch: refs/heads/master
  Home:   https://github.com/conformal/btcwire
  Commit: 7de20add63e82fda5b8adda82fc77b93f72985b9
      
https://github.com/conformal/btcwire/commit/7de20add63e82fda5b8adda82fc77b93f72985b9
  Author: Dave Collins <da...@conformal.com>
  Date:   2013-11-06 (Wed, 06 Nov 2013)

  Changed paths:
    M bench_test.go

  Log Message:
  -----------
  Add benchmark for writeBlockHeader.

This commit adds a benchmark for the writeBlockHeader function.