Refactor screen_init(), use methods developed in pimd project

- Refactor screen_init()
  - use native impl. of TTY probing from pimd project
    - check if TIOCWINSZ works
    - check if we're running in watch(1), for initctl
  - check if ANSI goto(999,999) escape seq. works (invasive)
  - fallback to 80x24
- Drop screen_exit()
- Rename screen_init() to get_width(), for now, matching pimd
- Relocate call in main() to banner(), first fn to write to TTY

Signed-off-by: Joachim Wiberg <troglobit@gmail.com>

configure.ac

@@ -32,7 +32,7 @@ AC_PROG_MKDIR_P
 
 # Configuration.
 AC_HEADER_STDC
-AC_CHECK_HEADERS([fstaby.h termios.h])
+AC_CHECK_HEADERS([fstaby.h termios.h sys/ioctl.h])
 AC_CHECK_FUNCS([strstr getopt getfsenty])
 
 # Check for uint[8,16,32]_t