Python bindings: various segfaults, should raise exception instead

[AllSeeingEyeTolledEweSew]

The following code snippets cause segfaults. Segfaults shouldn't ever happen in python.

• fs = file_storage(); fs.at(0): should raise IndexError
• fs = file_storage(); fs.at(-1): should raise IndexError
• fs = file_storage(); fs.symlink(0): should raise IndexError
• fs = file_storage(); fs.symlink(-1): should raise IndexError
• fs = file_storage(); fs.file_path(0): should raise IndexError
• fs = file_storage(); fs.file_path(-1): should raise IndexError
• fs = file_storage(); fs.file_name(0): should raise IndexError
• fs = file_storage(); fs.file_name(-1): should raise IndexError
• fs = file_storage(); fs.file_offset(0): should raise IndexError
• fs = file_storage(); fs.file_offset(-1): should raise IndexError
• fs = file_storage(); fs.file_flags(0): should raise IndexError
• fs = file_storage(); fs.file_flags(-1): should raise IndexError
• fs = file_storage(); fs.rename_file(0, "file.txt"): should raise IndexError
• fs = file_storage(); fs.rename_file(-1, "file.txt"): should raise IndexError
• fs = file_storage(); ct = create_torrent(fs); ct.set_hash(0, b"a" * 20): should raise IndexError
• fs = file_storage(); ct = create_torrent(fs); ct.set_hash(-1, b"a" * 20): should raise IndexError
• fs = file_storage(); ct = create_torrent(fs); ct.set_file_hash(0, b"a" * 20): should raise IndexError
• fs = file_storage(); ct = create_torrent(fs); ct.set_file_hash(-1, b"a" * 20): should raise IndexError
• session.add_torrent(torrent_info, any_arg=1): should raise TypeError
  • (for some reason it seems possible to invoke the deprecated form add_torrent(torrent_info, str, resume_data=..., storage_mode=..., paused=...), without the str positional arg)

I'm finished writing new unit tests and won't add any more items to this issue.