Clean out deprecated versioning variables
The merge request of the version branch was submitted a moment too soon.
Two version-related variables remained that are no longer needed, namely:
- one that indicated if the code is in beta-version;
- and another that told if the code was in a release branch.
The first was hardly ever used, while the second is not called for with the new repository layout. Both are removed from the code.
In addition, a Makefile bug is fixed that prevented compilation from sys_* directories.