Bonds prohibited except when approved by majority vote of electors. - Except for the purpose of refunding the existing outstanding indebtedness of the State and for assuming and refunding valid outstanding road improvement district bonds, the State of Arkansas shall issue no bonds or other evidence of indebtedness pledging the faith and credit of the State or any of its revenues for any purpose whatsoever, except by and with the consent of the majority of the qualified electors of the State voting on the question at a general election or at a special election called for that purpose.