Add socket handler & console client

This change adds a socket handler to the console-server, exposing a unix
domain socket for the UART data. We use this to replace the existing
stdio handler.

We also add a client for this socket, allowing multiple processes to
read/write data from & to the server.

Signed-off-by: Jeremy Kerr <jk@ozlabs.org>
diff --git a/Makefile b/Makefile
index ed46115..f076935 100644
--- a/Makefile
+++ b/Makefile
@@ -2,9 +2,12 @@
 CC = gcc
 CFLAGS = -Wall -Wextra -O2
 
-all: console-server
+all: console-server console-client
 
-console-server: console-server.o util.o stdio-handler.o log-handler.o
+console-server: console-server.o util.o \
+		log-handler.o socket-handler.o
+
+console-client: console-client.o util.o
 
 clean:
-	rm -f console-server *.o
+	rm -f console-server console-client *.o