Improvements to Courgette's version of bsdiff

* Store 'diff' bytes by run-length encoding zeros. This reduces the memory
  needed to store the zeros by ~30MB for chrome.7z.
* Store the control tuple elements in separate streams.  The 'extra_bytes'
  counts are often zero so this brings all the zeros together.

The uncompressed patch file is much smaller due to the run-length encoded
zeros.  It is slightly smaller (3-8%) after compression with lzma.

Review URL: http://codereview.chromium.org/115435

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@16343 0039d316-1c4b-4281-b951-d872f2087c98