Use experimental AutoDoc feature follow_package

Change doc/makedoc.g so that AutoDoc will read the code in roughly the
same order GAP processes it, leading to a more natural order for the
documentation.

doc/makedoc.g

@@ -3,7 +3,12 @@
 
 LoadPackage("AutoDoc");
 AutoDoc(rec(
-  autodoc := rec(files := ["README.md", "doc/chapters.autodoc"]),
+  autodoc := rec(
+      files := ["README.md", "doc/chapters.autodoc"],
+      scan_dirs := ["."],
+      scan_suffixes := ["g"],
+      follow_package := true
+  ),
   maketest := rec(name := "tst/AutoDoc_tests.g")
 ));