Add highlighting KEYWORDS for SQL PRODUCT.
PRODUCT should be a symbol, the name of a SQL product, such as
`oracle'. KEYWORDS should be a list; see the variable
`font-lock-keywords'. By default they are added at the beginning
of the current highlighting list. If optional argument APPEND is
`set', they are used to replace the current highlighting list.
If APPEND is any other non-nil value, they are added at the end
of the current highlighting list.
For example:
(sql-add-product-keywords 'ms
'(("\\b\\w+_t\\b" . font-lock-type-face)))
adds a fontification pattern to fontify identifiers ending in
`_t' as data types.
(fn PRODUCT KEYWORDS &optional APPEND)