Implements XRDP over vsock

1. Implements the ability to use AV_VSOCK for the transport rather than TCP.
2. Updates the ini file to be able to conditionally turn this feature on.

common/trans.h

@@ -27,6 +27,10 @@
 #define TRANS_MODE_TCP 1
 #define TRANS_MODE_UNIX 2
 
+#if defined(XRDP_ENABLE_VSOCK)
+#define TRANS_MODE_VSOCK 3
+#endif
+
 #define TRANS_TYPE_LISTENER 1
 #define TRANS_TYPE_SERVER 2
 #define TRANS_TYPE_CLIENT 3
@@ -62,7 +66,7 @@ struct source_info
 struct trans
 {
     tbus sck; /* socket handle */
-    int mode; /* 1 tcp, 2 unix socket */
+    int mode; /* 1 tcp, 2 unix socket, 3 vsock */
     int status;
     int type1; /* 1 listener 2 server 3 client */
     ttrans_data_in trans_data_in;