Potential Antimalarials. Part 20. Mannich Base Derivatives of 2-(7- Chloroquinolin-4-ylamino and 7-bromo(and 7-trifluoromethyl)-1,5- naphthyridin-4-ylamino)-4-chloro(or 4- or 6-t-butyl or 4- or 5-fluoro) phenols and 4(or 6)-t-Butyl-2-