Large rows cannot be read if packet_size exceeds max buffer size

In rev 147, there was a bug fix for bug #571579 - I am not able to view that bug report, but I assume it outlines a problem which we were also seeing (i.e. potential access of uninitialized memory from con->buffer_ptr). It appears though that there is a new bug introduced by that fix. For large rows, the amount of data in the packet may exceed the max size of our read buffer. In the following code, if our buffer is already full, but still we have not read con->packet_size worth of data, we will go to drizzle_state_read and attempt to read 0 bytes, which will return 0 and thus disconnect us.

drizzle_return_t drizzle_state_row_read(drizzle_con_st *con)
{
  drizzle_log_debug(con->drizzle, "drizzle_state_row_read");

  if (con->packet_size != 0 && con->buffer_size < con->packet_size)
  {
    drizzle_state_push(con, drizzle_state_read);
    return DRIZZLE_RETURN_OK;
  }

I believe the fix is to change the if statement above to read:

if (con->packet_size != 0 && con->buffer_size < con->packet_size && con->buffer_size < 5)

We only need up to 5 bytes of data for the purposes of drizzle_state_row_read, so this change would ensure we have enough to avoid any invalid memory accesses in this function, but leave the handling of large responses to other functions which are prepared to handle that.