start adding c structs for gates and ports

sim/port.lua

@@ -1,7 +1,7 @@
 
 PortTypes = {
 	output = 0,
-	input = 1
+	input = 1,
 }
 
 PortDirections = {
@@ -13,9 +13,20 @@ PortDirections = {
 	[5] = {0, 0, -1}
 }
 
-Port = {
-	logictype = 1,
-}
+Port = {}
+
+FFI.cdef[[
+	struct Gate;
+	struct Port {
+		bool state;
+		char type;
+		char direction;
+		bool causeupdate;
+		int position[3];
+		struct Gate* gate;
+		struct Net* group;
+	};
+]]
 
 function Port.new(self, type, direction, position, causeupdate, sim)
 	local o = {