Issue #2571695 by dawehner, plach, stefan.r, jaredsmith, lauriii, YesCT, xjm,...

Issue #2571695 by dawehner, plach, stefan.r, jaredsmith, lauriii, YesCT, xjm, catch, alexpott, joelpittet, Ryan Weal, Sutharsan, subhojit777, justAChris, nlisgo, effulgentsia, rpayanm, larowlan, chx, geertvd: Remove !placeholder and unsafe string return from SafeMarkup::format()