Merge upstream master.

- Includes -V option to see current ninja version (120514).
- Faster build_log loading.

TBR=maruel@chromium.org
Review URL: https://chromiumcodereview.appspot.com/10386135

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@137074 0039d316-1c4b-4281-b951-d872f2087c98