Assert for writing too many items to a container, or closing a container early.

[erichkeane]

When encoding, you start a container with either:
CBOR_API CborError cbor_encoder_create_array(CborEncoder *encoder, CborEncoder *arrayEncoder, size_t length);
CBOR_API CborError cbor_encoder_create_map(CborEncoder *encoder, CborEncoder *mapEncoder, size_t length);

The 'length' parameter can either be CborIndefiniteLength, or the actual value. When that length parameter is specified, it would be nice to have an assert (either on add, or on close?) that would confirm that the correct amount of items were written. It becomes pretty easy to forget to change the length when doing development, and it would be great to catch this rather than the otherwise unfortunate behaviors (such as failed finds in a map).

[thiagomacieira]

Good idea