feature: add devpts fd wrapper (#21)

This feature is intended to resolve devpts problem.

kernel/file_wrapper.h

@@ -0,0 +1,10 @@
+#include <linux/file.h>
+#include <linux/fs.h>
+
+struct ksu_file_wrapper {
+	struct file* orig;
+	struct file_operations ops;
+};
+
+struct ksu_file_wrapper* mksu_create_file_wrapper(struct file* fp);
+void mksu_delete_file_wrapper(struct ksu_file_wrapper* data);