Move rb_gc_verify_shareable to gc.c

Sync ruby/ruby@827f11f

Author: peterzhu2118

gc/gc.h

@@ -63,6 +63,7 @@ const char *rb_obj_info(VALUE obj);
 size_t rb_obj_memsize_of(VALUE obj);
 bool ruby_free_at_exit_p(void);
 void rb_objspace_reachable_objects_from_root(void (func)(const char *category, VALUE, void *), void *passing_data);
+void rb_gc_verify_shareable(VALUE);
 
 MODULAR_GC_FN unsigned int rb_gc_vm_lock(const char *file, int line);
 MODULAR_GC_FN void rb_gc_vm_unlock(unsigned int lev, const char *file, int line);

gc/mmtk/mmtk.c

@@ -1260,12 +1260,6 @@ rb_gc_impl_copy_attributes(void *objspace_ptr, VALUE dest, VALUE obj)
     rb_gc_impl_copy_finalizer(objspace_ptr, dest, obj);
 }
 
-bool
-rb_gc_impl_checking_shareable(void *ptr)
-{
-    return false;
-}
-
 // GC Identification
 
 const char *