Reload all source files that have been changed since they were
loaded. This predicate peforms the following steps:
- Compute the set of files that need to be reloaded.
- Call the hook prolog:
make_hook(before, Files)
- Reload the files
- Call the hook prolog:
make_hook(after, Files)
- If (4) fails, call list_undefined/0.
The hooks are called with an empty list if no files need
reloading.