Clean up th ecompile process by centralizing the include files

- code compile tested, but due to a yet unresolved problem with
          parse.h's creation, compile not completed...

src/include/executor/functions.h

@@ -0,0 +1,22 @@
+/*-------------------------------------------------------------------------
+ *
+ * functions.h--
+ *    
+ *
+ *
+ * Copyright (c) 1994, Regents of the University of California
+ *
+ * $Id: functions.h,v 1.1 1996/08/28 07:22:12 scrappy Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef	FUNCTIONS_H
+#define FUNCTIONS_H
+
+extern Datum ProjectAttribute(TupleDesc TD, TargetEntry *tlist,
+			      HeapTuple tup, bool *isnullP);
+
+extern Datum postquel_function(Func *funcNode, char **args,
+			       bool *isNull, bool *isDone);
+
+#endif /* FUNCTIONS_H */