cpp hygiene in the vm

* libguile/vm-engine.c:
* libguile/vm-i-scheme.c:
* libguile/vm-i-system.c: CPP hygiene: the code that #defines, #undefs.
  Makes things cleaner given the multiple inclusion dance we do.

libguile/vm-engine.c

@@ -433,8 +433,34 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
   abort (); /* never reached */
 }
 
+#undef ALIGNED_P
+#undef CACHE_REGISTER
+#undef CHECK_OVERFLOW
+#undef FREE_VARIABLE_REF
+#undef FUNC2
+#undef INIT
+#undef INUM_MAX
+#undef INUM_MIN
+#undef jump_table
+#undef LOCAL_REF
+#undef LOCAL_SET
+#undef NEXT
+#undef NEXT_JUMP
+#undef REL
+#undef RETURN
+#undef RETURN_ONE_VALUE
+#undef RETURN_VALUE_LIST
 #undef RUN_HOOK
 #undef RUN_HOOK1
+#undef SYNC_ALL
+#undef SYNC_BEFORE_GC
+#undef SYNC_IP
+#undef SYNC_REGISTER
+#undef VARIABLE_BOUNDP
+#undef VARIABLE_REF
+#undef VARIABLE_SET
+#undef VM_DEFINE_OP
+#undef VM_INSTRUCTION_TO_LABEL
 #undef VM_USE_HOOKS
 
 /*