Set the first version component to be the same as the last Subversion-based
release build version and add two more components (major and minor version
numbers). To allow for nightly build updates this should probably include
another component (e.g. build timestamp), but we're not there yet.
Store full revision hash in REVISION file. Write fixes 10 chars of revision
hash to version.h. Use `#pragma once` in version.h. Support getting revision
from TeamCity environment variable (similar to Jenkins).
Mike Gelfand