Add RVALUE_OLD_AGE to GC::INTERNAL_CONSTANTS for MMTk

Author: peterzhu2118

gc/mmtk/mmtk.c

@@ -550,6 +550,8 @@ rb_gc_impl_init(void)
     rb_hash_aset(gc_constants, ID2SYM(rb_intern("RVARGC_MAX_ALLOCATE_SIZE")), LONG2FIX(MMTK_MAX_OBJ_SIZE));
     // Pretend we have 5 size pools
     rb_hash_aset(gc_constants, ID2SYM(rb_intern("SIZE_POOL_COUNT")), LONG2FIX(5));
+    // TODO: correctly set RVALUE_OLD_AGE when we have generational GC support
+    rb_hash_aset(gc_constants, ID2SYM(rb_intern("RVALUE_OLD_AGE")), INT2FIX(0));
     OBJ_FREEZE(gc_constants);
     rb_define_const(rb_mGC, "INTERNAL_CONSTANTS", gc_constants);