The attached patch solves the problem raised by http://www.redmine.org/boards/1/topics/34344

A new global setting under the project tab (which by default leaves the current behavior) allows to specify if the administrator wants to list other projects' shared versions to users that do not belong to the original versions' project.

This solves IMHO a security issue since version names (if used e.g. as contracts) could be nicely shared e.g. to an upper level "control panel" project, but only to users that have visibility to the specific projects.

Contracts, and more importantly their custom attributes, advancement and number of open issues, could be sensible information not to disclose to everybody.

The patch applies over version 2.3.1