identify dialogs via official serial and maintain as result message;
clarified Protocol.is_inlined: suppress result/tracing/state messages uniformly;
cumulate_markup/select_markup depending on command state;
explicit Rendering.output_messages;
tuned source structure;
src/Pure
src/FOL
src/HOL
src/ZF
src/CCL
src/CTT
src/Cube
src/FOLP
src/LCF
src/Sequents
src/Doc