CoqIDE ported to the revides protocol

- the zone to be edited is now between the marks
  start_of_input and stop_of_input
- when -debug is given, the edit zone is underlined
- the cmd_stack is focused/unfocused according to the new protocol
- read only tag resurrected and used to block the "Qed" ending
  a focused zone
STM: some refactoring, support revised CoqIDE protocol
fixtest
wg_Session: fix copy/paste of tagged text
wg_Command: less ugly query pane