a partial support for def rules in the C runtime

The def rules are now compiled to byte code by the compiler and then to
native code by the JIT compiler in the runtime. Not all constructions
are implemented yet. The partial implementation is now in the repository
but it is not activated by default since this requires changes in the
PGF format. I will enable it only after it is complete.

src/runtime/c/pgf/pgf.h

@@ -17,44 +17,24 @@ extern GU_DECLARE_TYPE(PgfExn, abstract);
 extern GU_DECLARE_TYPE(PgfParseError, abstract);
 extern GU_DECLARE_TYPE(PgfTypeError, abstract);
 
-/// @name PGF Grammar objects
-/// @{
-
 typedef struct PgfPGF PgfPGF;
 
 typedef struct PgfConcr PgfConcr;
 
-
-/**< A representation of a PGF grammar. 
- */
-
 #include <pgf/expr.h>
 #include <pgf/graphviz.h>
 
-/// An enumeration of #PgfExpr elements.
 typedef GuEnum PgfExprEnum;
 
 PgfPGF*
 pgf_read(const char* fpath,
          GuPool* pool, GuExn* err);
 
-/**< Read a grammar from a PGF file.
- *
- * @param from  PGF input stream.
- * The stream must be positioned in the beginning of a binary
- * PGF representation. After a succesful invocation, the stream is
- * still open and positioned at the end of the representation.
- *
- * @param[out] err_out  Raised error.
- * If non-\c NULL, \c *err_out should be \c NULL. Then, upon
- * failure, \c *err_out is set to point to a newly allocated
- * error object, which the caller must free with #g_exn_free
- * or #g_exn_propagate.
- *
- * @return A new PGF object, or \c NULL upon failure. The returned
- * object must later be freed with #pgf_free.
- *
- */
+void
+pgf_concrete_load(PgfConcr* concr, GuIn* in, GuExn* err);
+
+void
+pgf_concrete_unload(PgfConcr* concr);
 
 GuString
 pgf_abstract_name(PgfPGF*);
@@ -176,8 +156,6 @@ pgf_concr_add_literal(PgfConcr *concr, PgfCId cat,
                       PgfLiteralCallback* callback,
                       GuExn* err);
 
-/// @}
-
 void
 pgf_print(PgfPGF* pgf, GuOut* out, GuExn* err);