add doxygen configuration

doc/html/files_dup.js

@@ -0,0 +1,8 @@
+var files_dup =
+[
+    [ "config.c", "config_8c.html", "config_8c" ],
+    [ "config.h", "config_8h.html", "config_8h" ],
+    [ "file.c", "file_8c.html", "file_8c" ],
+    [ "file.h", "file_8h.html", "file_8h" ],
+    [ "test.c", "test_8c.html", "test_8c" ]
+];