I've noticed various terminal emulators that need to obtain a sane
default termios structure use very complex `hacks'. Even though POSIX
doesn't provide any functionality for this, extend our termios API with
cfmakesane(3), which is similar to the commonly supported cfmakeraw(3),
except that it fills the termios structure with sane defaults.
Change all code in our base system to use this function, instead of
depending on <sys/ttydefaults.h> to provide TTYDEF_*.
The <sys/termios.h> header file is hardlinked to <termios.h>. It
contains both the structures and the flag definitions, but also the C
library interface that's implemented by the C library.
This header file has the typical problem of including too many random
things and being badly ordered. Instead of trying to fix this, decompose
it into two header files:
- <sys/_termios.h>, which contains struct termios and the flags.
- <termios.h>, which includes <sys/_termios.h> and contains the C
library interface.
This means userspace has to include <termios.h> for struct termios,
while kernelspace code has to include <sys/tty.h>. Also add a
<sys/termios.h>, which prints a warning message before including
<termios.h>. I am aware that there are some applications that use this
header file as well.
