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>

plugins/Makefile

@@ -4,7 +4,7 @@ CPPFLAGS   += -I..
 LDFLAGS    := $(filter-out -rdynamic, $(LDFLAGS))
 LDFLAGS    += -shared
 PLUGINS    ?= initctl.so alsa-utils.so bootmisc.so dbus.so hwclock.so \
-	      resolvconf.so urandom.so x11-common.so
+	      resolvconf.so urandom.so x11-common.so tty.so
 DEPS        = $(addprefix .,$(PLUGINS:.so=.d))
 
 include ../common.mk