BUG: Match exception declarations between scipy/io/matlab/streams.pyx and
scipy/io/matlab/streams.pxd to prevent an error in recent versions of
cython.
BUG: Raise exceptions when an invalid file position is returned.
Merge pull request #4084 from insertinterestingnamehere/cython_fix

BUG: Match exception declarations in scipy/io/matlab/streams.pyx to their corresponding pxd declarations.