Turn on compiler deprecation warnings.
Since we are renaming and moving methods around, following a policy of deprecation if the method has been in use for a while, we need a way to make sure we eventually remove any references to the deprecated versions, in case we missed some while refactoring (which is easy to do if different projects reference different library versions). Turn on compiler warnings for calling deprecated API methods. This is probably done using the <showDeprecation> option of the Maven Compiler Plugin.
Hmmm… maybe this is already turned on to some extent. I'm seeing things like this:
However here IOKit extends URIAccessible, which is deprecated; but IOKit is itself deprecated, so here is a case in which we would actually not want to see a warning, as deprecated things are likely to call other deprecated things, and there's no use in "fixing" this if we're going to get rid of the whole hierarchy anyway.
This should probably be tested on a couple of libraries, first; there may be more deprecation warnings than we want starting out, especially for legacy code that has been incorporated into a repository but not yet fully updated. In those cases the short-term solution may be simply to disable this option in that particular submodule.