2) Implement some options for SQLGetDescField().
3) Handle *Inifinity* timestamp for SQL_C_CHAR type output.
4) Separate Unicode conversions from common implementations.
5) Improve internal parse_statement() function.
1) Prepare to separate 4 kinds of Descriptor handles.
2) Detect the transaction status more naturally.
3) Improve Parse Statement functionality for the use
of updatable cursors.
4) Improve updatable cursors.
5) Implement SQLGetDescField() and improve SQLColAttribute().
6) etc.