tty: Add handler for local tty mirroring

This change adds a simple handler for mirroring data to local tty
device, like a hardware UART.

This is specified through a new config parameter 'local-tty'.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
diff --git a/Makefile.am b/Makefile.am
index 5f0a1bb..2df24d8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -34,6 +34,7 @@
 	 config.c \
 	 log-handler.c \
 	 socket-handler.c \
+	 tty-handler.c \
 	 console-socket.c
 
 obmc_console_client_SOURCES = \