Fix #91: Add support for tty nologin, to start /bin/sh immediately

This patch adds a `nologin` flag to the `tty` configuration directive,
making it possible to set up really simple embedded systems with no
login.

Example, put the following line in `/etc/finit.d/getty.conf` to get
a "Please press Enter to ..." prompt before being presented with a
root shell prompt.

    tty [12345] @console noclear nologin

Needless to say, this is not very secure, but can be really useful
for developer setups, during board bringup, or similar.

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

src/tty.h

@@ -38,6 +38,7 @@ typedef struct {
 	char  *term;
 	int    noclear;
 	int    nowait;
+	int    nologin;
 	int    runlevels;
 
 	char  *cmd;		/* NULL when running built-in getty */