Add some types to fixed types.

Some bindings where not handled in a switch

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>
Refactor a bit _bcp_exec_out

- do not use multiple buffers for conversion, reduce memory needed
- do not use bcp_column_data, buffers are not reused so avoid to allocate
  for each row
- allocate a minimum buffer, so to make easier to compute buffer size
  for fixed bytes
- move variable in nested scopes making easier to understand where they
  are used

Signed-off-by: Frediano Ziglio <freddy77@gmail.com>