Changed version to 1.2.1.

Changed version to 1.2.1.
(sql-pop-to-buffer-after-send-region): Improved documentation.
(sql-mysql-program): Added MySQL support.
(sql-prompt-length): Made prompt-length configurable.
(sql-mode-syntax-table): Made apostrophe (') be a string delimiter.
(sql-help): Added MySQL support, changed documentation.
(sql-send-region): A message is displayed if something is sent.
(sql-mode): Added buffer-local comment-start.
(sql-interactive-mode): Use sql-prompt-length to set left-margin.
(sql-interactive-mode): Added buffer-local comment-start.
(sql-oracle): Set sql-prompt-length.
(sql-sybase): Set sql-prompt-length.
(sql-mysql): Added MySQL support.
(sql-ingres): Set sql-prompt-length.
(sql-ms): Set sql-prompt-length.
(sql-postgres): Set sql-prompt-length.