Have all allocate statements pass out "stat" values that are then checked

Whenever an `allocate` statement is used, it should be made to pass out a `stat` value, that is then checked for success conditions. If the `allocate` was un-successful, then `endrun` should be called, with the associated message containing the `stat` value.

Although this might require modifications across CAMDEN, it will make model failures related to allocations much easier to identify and debug, which should help both users and developers.

Search CAMDEN for every allocate statement and review how endrun is called for allocation failures. Update each allocation path so its stat value is checked and included in the associated endrun message; completion means all allocation statements follow this behavior. No specific files or tests are named, so begin with a repository-wide search for allocate and endrun.

Written by the indexing model from the issue text.