add dummy 'add2lib' target to Grammar/Makefile so non-GNU makes don't bail out

This closes patch:
http://sourceforge.net/patch/index.php?func=detailpatch&patch_id=101176&group_id=5470

Grammar/Makefile

@@ -6,6 +6,9 @@ DESTC=		$(TOP)/Python/graminit.c
 
 all:		install
 
+# This target is used by the master Makefile to add the objects to the library
+add2lib:
+
 install:	$(DESTH) $(DESTC)
 
 depend: