Refactor TTY code to honor runlevels and use I/O plugin to watch /dev

Add support for runlevels to tty command and support for reading baud
rate and TERM variable from finit.conf.

The tty-watcher thread has been converted to a standard I/O plugin.

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

Makefile

@@ -34,8 +34,7 @@ ARCHIVE     = $(PKG).tar.xz
 EXEC        = finit reboot
 HEADERS     = plugin.h svc.h helpers.h queue.h
 DISTFILES   = LICENSE README ChangeLog finit.conf services
-OBJS        = finit.o conf.o helpers.o sig.o svc.o plugin.o
-OBJS       += tty.o
+OBJS        = finit.o conf.o helpers.o sig.o svc.o plugin.o tty.o
 SRCS        = $(OBJS:.o=.c)
 DEPS        = $(addprefix .,$(SRCS:.c=.d))