Searchable behavior's batchUpdateIndex fails if a table has a composite primary key.

You will get the following error when you try to batchUpdateIndex a table with composite key:

Fatal error: Uncaught exception 'ErrorException' with message 'strpos() expects parameter 1 to be string, array given' in library/Doctrine/Connection.php:725

Here's the full stack trace:

Stack trace:
#0 [internal function]: Bootstrap->errorHandler(2, 'strpos() expect...', '/Users/reko/Sit...', 725, Array)
#1 /Users/reko/Sites/MyProject/library/Doctrine/Connection.php(725): strpos(Array, '.')
#2 /Users/reko/Sites/MyProject/library/Doctrine/Search.php(246): Doctrine_Connection->quoteIdentifier(Array)
#3 /Users/reko/Sites/MyProject/library/Doctrine/Template/Searchable.php(69): Doctrine_Search->batchUpdateIndex(NULL, NULL, NULL)
#4 /Users/reko/Sites/MyProject/library/Doctrine/Template/Searchable.php(81): Doctrine_Template_Searchable->batchUpdateIndex(NULL, NULL, NULL)
#5 [internal function]: Doctrine_Template_Searchable->batchUpdateIndexTableProxy()
#6 /Users/reko/Sites/MyProject/library/Doctrine/Record.php(2622): call_user_func_array(Array, Array)
#7 [internal function]: Doctrine_Record->__call('batchUpdateInde...', Array)
#8 [internal function]: In in /Users/reko/Sites/MyProject/library/Doctrine/Connection.php on line 725

I know that it's recommended that you don't use composite primary keys, but this happens to occur when you stack the I18n and Searchable behaviour together, since the Translation table I18n behavior creates uses a composite key on (id, lang).

Anyways, the bug was quite simple one to fix and I've attached a patch that fixes the issue.