Fix: Use correct syntax of date into sql requests (with quotes)

htdocs/accountancy/class/accountancyaccount.class.php

htdocs/accountancy/class/accountancysystem.class.php

htdocs/adherents/index.php

htdocs/adherents/type.php

htdocs/bookmarks/class/bookmark.class.php

htdocs/comm/mailing/class/mailing.class.php

htdocs/compta/localtax/class/localtax.class.php

htdocs/compta/paiement/cheque/class/remisecheque.class.php

htdocs/compta/paiement/class/paiement.class.php

htdocs/compta/prelevement/class/bonprelevement.class.php

htdocs/compta/prelevement/class/rejetprelevement.class.php

htdocs/compta/salaries/class/paymentsalary.class.php

htdocs/compta/tva/class/tva.class.php

htdocs/contrat/class/contrat.class.php

htdocs/contrat/liste.php

htdocs/contrat/services.php

htdocs/core/class/discount.class.php

htdocs/core/class/events.class.php

htdocs/core/class/notify.class.php

htdocs/core/db/pgsql.class.php