Fix a bug in the installer caused by r77487 creating installer sql statements like...

Fix a bug in the installer caused by r77487 creating installer sql statements like "GRANT ALL PRIVILEGES ON `'dbname'`.* TO ''tablename''@'%" while improving the database independence of replaceVars.

* Drop unused and likely broken /*$var*/` -> `$var syntax
* Replace {$var} with '{$var}' and `{$var}` handling that uses relevant database independent quoting ({$var} without surrouding quotes are never used)
* Give the generic/mysql class a proper quote_ident implementation
* Fix the unused Oracle and Sqlite quote_ident implementations which are potential sql injections if used
* Split common variable replacemnt code off to a replaceGlobalVars and make the generic and oracle code use it instead of duplicating the same code as each other