Fix issue with VINTR, VEOF et al not being restored after boot

On Alpine Linux 3.6 the tcsetattr() calls failed.  This turned out to be
a deeply rooted issue not limited to just musl libc.  The workaround is
to call tcsetattr() in several rounds.  In particular the modem signals,
c_cflag bits, always fail, so we take a bet on Linux having set up the
terminals (hope as a strategy) and ignore that problem, for now.

Also, use TCSAFLUSH with tcsetattr(), that seems to work better and is
what BusyBox stty use.

The local CTL() macro is replaced with CTL() from ttydefaults.h, which
exists also in musl libc.

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

src/getty.c

@@ -41,7 +41,6 @@
 #define _PATH_LOGIN  "/bin/login"
 #endif
 
-#define CTL(x)   ((x) ^ 0100)
 #define print(s) (void)write(STDOUT_FILENO, s, strlen(s))
 
 
@@ -164,7 +163,7 @@ static void do_getty(char *tty, char *name, size_t len)
 
 		np = name;
 		while ((ch = readch(tty)) != '\n') {
-			if (ch == CTL('U')) {
+			if (ch == CTRL('U')) {
 				while (np > name) {
 					(void)write(1, "\b \b", 3);
 					np--;
@@ -290,9 +289,9 @@ int sh(char *tty)
 	/* Reenable Ctrl-D and Ctrl-C, and ... */
 	if (!tcgetattr(STDIN_FILENO, &term)) {
 		term.c_lflag    |= ISIG;
-		term.c_cc[VEOF]  = CTL('D');
-		term.c_cc[VINTR] = CTL('C');
-		tcsetattr(STDIN_FILENO, TCSANOW, &term);
+		term.c_cc[VEOF]  = CEOF;
+		term.c_cc[VINTR] = CINTR;
+		tcsetattr(STDIN_FILENO, TCSAFLUSH, &term);
 	}
 
 	/* ... unblock signals in general */