Support of local modes and control characters is now centralized in
generic TTY driver (line control is working well on VTs).
Implementation of the new TTY input interface is done only for VTs.

for now, envp (a NULL terminated char* array) is given to userspace by
3rd main argument, and may be NULL if no environment is used

Stack area is used to store argv[] data, and it is now possible to have
4 pages (default) of stack to store arguments.
The new algorithm is quite heavy, but really more flexible and reliable.