Use put_data function to send data to server

In protocol 7+ data are sent more or less with same encoding used to send
parameters so reuse the same code.
It actually require some hacks but I'm planning to remove bcp_column_data
entirely and use column_cur_size and column_data instead.

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

Use simpler tight loop.

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