Conhost improvements.
This MR serves as prerequistes for two open (in progress) MR:
- we don't properly handle ctrl-c in ReadConsole with control block
- this revisits ctrl-break (or ctrl-break from unix console) to map it unconditionnaly of console mode (as native does) to a windows ctrl event
- and transfer to windows layers the management of ctrl-c (for a unix console when ENABLE_PROCESSED_INPUT isn't set)
- add ASC in win32 edit mode to completely clear the current editi buffer