Major change to sequencer API.

Major change to sequencer API.

The sequencer API is totally recoded with the style of "encapsulation"
in other api.
The structure becomes opaque and accessed only via functions.

Other changes:
- There is no longer group in client and port info.
- snd_seq_query_subs_t is renamed to snd_seq_query_subscribe_t.
- snd_seq_delete_port takes only the port id argument instead of
  port_info structure.
- snd_seq_input/output_buffer_size are renamed
  as snd_seq_get_input/output_buffer_size.
  Similarly snd_seq_resize_input/output_buffer are renamed as
  snd_seq_set_input/output_buffer_size.
- snd_seq_get_named_queue is renamed to snd_seq_query_named_queue.
- Sync codes are removed temporarily from API.
- Subscription conditions are accessed via the corresponding functions.
  convert_time is named now as time_update.
- snd_seq_get/set_queue_owner are removed.
  Use snd_seq_get/set_queue_info instead.
- Instrument put/get/remove structure is unified as snd_instr_header_t.