Provide git-cl upload and dcommit hooks based on this
single hooks file.  Installed via git-cl config.
Loads and calls the PresubmitSupport library.
Test failure before a dcommit halts the check-in.

BUG=5339
TEST=hooks file runs presubmit checks and halts
checkin (dcommit) or repeats error messages (upload).
hooks file runs and doesn't interrupt process if no
errors present.
Review URL: http://codereview.chromium.org/256075

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@28125 0039d316-1c4b-4281-b951-d872f2087c98