Add soft assertions for regexp patterns

Change-Id: If0072f8f9761bdc34b35d01aac4d00c5391b8a20
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@digia.com>
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>
LdParser: Do not consider "first defined here" as an error

Change-Id: I01b27cd12776e22a5b52ceae4c89a4cd567c69ed
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>