Added the ui-socket.h.

Two new issues to solve:

* Should the ui communication component also be the one that manages
  permissions?
* The format of data sent (protocol) needs definition.

sources/ui-socket.h

@@ -0,0 +1,19 @@
+
+/*
+ * Interface for controlling communication with the UI.
+ */
+
+#ifndef UI_SOCKET_H
+#define UI_SOCKET_H
+
+struct process_info {
+  // TODO: define some fields
+};
+
+int init_ui_socket();
+
+// TODO: design an interface for asking user for permission.
+
+int ask_access(const char *filename, process_info pi);
+
+#endif // !UI_SOCKET_H