(sql-product-alist): Rename variable `sql-product-support'.

(sql-product-alist): Rename variable `sql-product-support'.
Add Postgres login parameters.
(sql-set-product, sql-product-feature): Update with renamed variable.
(sql-connect-postgres): Add username prompt.
(sql-imenu-generic-expression, sql-mode-font-lock-object-name):
Make patterns less product specific.
(sql-xemacs-p, sql-emacs19-p): Add flags for emacs variants.
(sql-mode-abbrev-table): Modify initialization.
(sql-builtin-face): Add variable.
(sql-keywords-re): Add macro.
(sql-mode-ansi-font-lock-keywords): Update for ANSI-92.
(sql-mode-oracle-font-lock-keywords): Update for Oracle 9i.
(sql-mode-postgres-font-lock-keywords): Update for Postgres 7.3.
(sql-mode-mysql-font-lock-keywords): Update for MySql 4.0.
(sql-mode-linter-font-lock-keywords)
(sql-mode-ms-font-lock-keywords): Use `sql-keywords-re' macro.
(sql-mode-sybase-font-lock-keywords, sql-mode-informix-font-lock-keywords)
(sql-mode-interbase-font-lock-keywords, sql-mode-ingres-font-lock-keywords)
(sql-mode-solid-font-lock-keywords, sql-mode-sqlite-font-lock-keywords)
(sql-mode-db2-font-lock-keywords): Default to nil.
(sql-product-font-lock): Always highlight ANSI keywords.
(sql-add-product-keywords): Made similar to `font-lock-add-keywords'.
(sql-send-string): Add function.