Add LOCALTIME and LOCALTIMESTAMP functions per SQL99 standard.

Remove ODBC-compatible empty parentheses from calls to SQL99 functions
 for which these parentheses do not match the standard.
Update the ODBC driver to ensure compatibility with the ODBC standard
 for these functions (e.g. CURRENT_TIMESTAMP, CURRENT_USER, etc).
Include a new appendix in the User's Guide which lists the labeled features
 for SQL99 (the labeled features replaced the "basic", "intermediate",
 and "advanced" categories from SQL92). features.sgml does not yet split
 this list into "supported" and "unsupported" lists.