When camlp4 is used as a preprocessor, nothing after an "include" in a
signature gets passed to ocamlc.  Here's a patch to fix it:

*** camlp4/ast2pt.ml	Tue Dec  1 08:19:34 1998
--- ast2pt.ml	Thu Feb 25 18:17:10 1999
***************
*** 505,509 ****
    | SgExt loc n t p ->
        [mksig loc (Psig_value (shd n) (mkvalue_desc t p)) :: l]
!   | SgInc loc mt -> [mksig loc (Psig_include (module_type mt))]
    | SgMod loc n mt -> [mksig loc (Psig_module (shd n) (module_type mt)) :: l]
    | SgMty loc n mt ->
--- 505,509 ----
    | SgExt loc n t p ->
        [mksig loc (Psig_value (shd n) (mkvalue_desc t p)) :: l]
!   | SgInc loc mt -> [mksig loc (Psig_include (module_type mt)) :: l]
    | SgMod loc n mt -> [mksig loc (Psig_module (shd n) (module_type mt)) :: l]
    | SgMty loc n mt ->