Use macros for creating the intermediate stage.

This is to make it easier to change function signatures by consolidating the places where the signatures exist.

src/intermediate/mod.rs

@@ -32,6 +32,7 @@ mod keyword;
 mod latex_environment;
 mod latex_fragment;
 mod line_break;
+mod macros;
 mod object;
 mod org_macro;
 mod page;