Update, changelog, setup.py, and submodules for 3.39 release.
Update, changelog, setup.py, and submodules for 3.39 release.

dtjackson/gsutil,craigcitro/gsutil,mattdr/gsutil,BrandonY/gsutil,ttiurani/gsutil,GoogleCloudPlatform/gsutil,chriskuehl/gsutil-debian,dimfeld/gsutil,fishjord/gsutil,GoogleCloudPlatform/gsutil