[m-rev.] diff: add missing function prototype for mercury_init_grade_check()

[Julien Fischer]

Add missing function prototype for mercury_init_grade_check().

runtime/mercury_init.h:
      As above.

Julien.

diff --git a/runtime/mercury_init.h b/runtime/mercury_init.h
index 7bfb5ce..9c51908 100644
--- a/runtime/mercury_init.h
+++ b/runtime/mercury_init.h
@@ -59,6 +59,12 @@ extern  void    mercury_call_main(void);

  extern  int     mercury_terminate(void);

+// mercury_init_grade_check is defined in the <module>_init.c file.
+// It is used to ensure that everything gets compiled in the same grade.
+// See mercury_grade.h for details.
+
+extern const char *mercury_init_grade_check(void);
+
  ////////////////////////////////////////////////////////////////////////////

  // This part defines things which are used by the automatically