All outstanding indebtedness against the City of Austin, either in the form of bonds, refunded bonds, certificates of indebtedness, or orders issued by the city council of said city and which is now unpaid, no matter for what purpose the same was created and whether created under and by virtue of general or special laws, or by the city council in the due course of its business, and whether at the time the same was incurred it was legally incurred or not, is hereby declared to be a legal, valid and existing indebtedness against the City of Austin, and the faith and credit of said city is hereby irrevocably pledged to the payment thereof.