Analyzing module for importing `Unsafe` module
----------------------------------------------

The `UnsafeModule` analysis returns information whether a module is unsafe,
i.e., it imports directly or indirectly the module `System.IO.Unsafe`
(or other modules containing `Unsafe` in their name).
Such modules might hide dangerous operations in
purely functional operations.

The result of this analysis is the list of the names of all modules
which directly imports the module `System.IO.Unsafe`.
Thus, a module is safe if the analysis result is the empty list.