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>

src/log.c

@@ -50,9 +50,7 @@ void log_exit(void)
 	 * Unless in debug mode at shutdown, Reinitialize screen,
 	 * terminal may have been resized at runtime
 	 */
-	if (debug)
-		screen_exit();
-	else
+	if (!debug)
 		screen_init();
 
 	enable_progress(1);
@@ -79,7 +77,6 @@ void log_debug(void)
 
 	if (debug) {
 		loglevel = LOG_DEBUG;
-		screen_exit();
 	} else {
 		loglevel = LOG_NOTICE;
 		screen_init();