SQL Mode 2.7: Code cleanup and primatives for SQL redirection

SQL Mode 2.7: Code cleanup and primatives for SQL redirection

	* progmodes/sql.el: Version 2.7.
	(sql-buffer-live-p): Improve detection.
	(sql-find-sqli-buffer, sql-set-sqli-buffer-generally)
	(sql-set-sqli-buffer): Use it.
	(sql-product-interactive): Run `sql-set-sqli-hook'.
	(sql-rename-buffer): Code cleanup.
	(sql-redirect, sql-redirect-value): New functions.  More to come.