Mayor Thomas M. Menino plans to call for a major overhaul of Boston’s faltering vocational high school, seeking broad authority to create a job training institution that aims to help teenagers and adults climb out of poverty and into the middle class. By day, the new Madison Park Technical Vocational High School would serve high school students, coupling real-world job skills and rigorous academics. By night, adults would take to the same classrooms, workshops, and laboratories to develop skills for the modern workforce. For the mayor, who is set to unveil the initiative in his State of the City speech at Faneuil Hall, it is a chance to leave a legacy of job creation.