Improve Data I/O

Reading data from UTF-8 capable drivers now works. However
SqlExecDirect is not an ideal solution to write date into the
database. It's better to use the binding API.

UnixOdbc:

- Use uint8[] to receive character data. This will only work properly
  when the ODBC driver uses UTF-8 as the ANSI encoding. This could be
  solved better using IConv conversion.

UnixOdbcLL:

- Rename DataType to CDataType and introduce a new DataType enum. SQL_
  now maps to DataType and SQL_C_ now maps to CDataType.

- Change various cnames to the ODBC defined data types rather then the
  real C types.

- Add SQLPrepare

- Add SQLExecute

- Add SQLBindParameter