Always raise TypeError for wrong argument types

Put declarations on separate line to avoid warnings like this:

  Non-trivial type declarators in shared declaration (e.g. mix
  of pointers and values). Each pointer declaration should be
  on its own line.

The code that checks whether hooks are callable() (and some other type
checks) should always raise TypeError on failure. Before this change,
both ValueError and TypeError were used in an inconsistent way (C
extension and Python implementation were not the same).